/* * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.nio.file; import java.nio.file.attribute.*; import java.nio.file.spi.FileSystemProvider; import java.nio.file.spi.FileTypeDetector; import java.nio.channels.SeekableByteChannel; import java.io.InputStream; import java.io.OutputStream; import java.io.Reader; import java.io.Writer; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.io.IOException; import java.util.*; import java.security.AccessController; import java.security.PrivilegedAction; import java.nio.charset.Charset; import java.nio.charset.CharsetDecoder; import java.nio.charset.CharsetEncoder; /** * This class consists exclusively of static methods that operate on files, * directories, or other types of files. * *

In most cases, the methods defined here will delegate to the associated * file system provider to perform the file operations. * * @since 1.7 */ public final class Files { private Files() { } /** * Returns the {@code FileSystemProvider} to delegate to. */ private static FileSystemProvider provider(Path path) { return path.getFileSystem().provider(); } // -- File contents -- /** * Opens a file, returning an input stream to read from the file. The stream * will not be buffered, and is not required to support the {@link * InputStream#mark mark} or {@link InputStream#reset reset} methods. The * stream will be safe for access by multiple concurrent threads. Reading * commences at the beginning of the file. Whether the returned stream is * asynchronously closeable and/or interruptible is highly * file system provider specific and therefore not specified. * *

The {@code options} parameter determines how the file is opened. * If no options are present then it is equivalent to opening the file with * the {@link StandardOpenOption#READ READ} option. In addition to the {@code * READ} option, an implementation may also support additional implementation * specific options. * * @param path * the path to the file to open * @param options * options specifying how the file is opened * * @return a new input stream * * @throws IllegalArgumentException * if an invalid combination of options is specified * @throws UnsupportedOperationException * if an unsupported option is specified * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. */ public static InputStream newInputStream(Path path, OpenOption... options) throws IOException { return provider(path).newInputStream(path, options); } /** * Opens or creates a file, returning an output stream that may be used to * write bytes to the file. The resulting stream will not be buffered. The * stream will be safe for access by multiple concurrent threads. Whether * the returned stream is asynchronously closeable and/or * interruptible is highly file system provider specific and * therefore not specified. * *

This method opens or creates a file in exactly the manner specified * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel} * method with the exception that the {@link StandardOpenOption#READ READ} * option may not be present in the array of options. If no options are * present then this method works as if the {@link StandardOpenOption#CREATE * CREATE}, {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, * and {@link StandardOpenOption#WRITE WRITE} options are present. In other * words, it opens the file for writing, creating the file if it doesn't * exist, or initially truncating an existing {@link #isRegularFile * regular-file} to a size of {@code 0} if it exists. * *

Usage Examples: *

     *     Path path = ...
     *
     *     // truncate and overwrite an existing file, or create the file if
     *     // it doesn't initially exist
     *     OutputStream out = Files.newOutputStream(path);
     *
     *     // append to an existing file, fail if the file does not exist
     *     out = Files.newOutputStream(path, APPEND);
     *
     *     // append to an existing file, create file if it doesn't initially exist
     *     out = Files.newOutputStream(path, CREATE, APPEND);
     *
     *     // always create new file, failing if it already exists
     *     out = Files.newOutputStream(path, CREATE_NEW);
     * 
* * @param path * the path to the file to open or create * @param options * options specifying how the file is opened * * @return a new output stream * * @throws IllegalArgumentException * if {@code options} contains an invalid combination of options * @throws UnsupportedOperationException * if an unsupported option is specified * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. The {@link * SecurityManager#checkDelete(String) checkDelete} method is * invoked to check delete access if the file is opened with the * {@code DELETE_ON_CLOSE} option. */ public static OutputStream newOutputStream(Path path, OpenOption... options) throws IOException { return provider(path).newOutputStream(path, options); } /** * Opens or creates a file, returning a seekable byte channel to access the * file. * *

The {@code options} parameter determines how the file is opened. * The {@link StandardOpenOption#READ READ} and {@link * StandardOpenOption#WRITE WRITE} options determine if the file should be * opened for reading and/or writing. If neither option (or the {@link * StandardOpenOption#APPEND APPEND} option) is present then the file is * opened for reading. By default reading or writing commence at the * beginning of the file. * *

In the addition to {@code READ} and {@code WRITE}, the following * options may be present: * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Option Description
{@link StandardOpenOption#APPEND APPEND} If this option is present then the file is opened for writing and * each invocation of the channel's {@code write} method first advances * the position to the end of the file and then writes the requested * data. Whether the advancement of the position and the writing of the * data are done in a single atomic operation is system-dependent and * therefore unspecified. This option may not be used in conjunction * with the {@code READ} or {@code TRUNCATE_EXISTING} options.
{@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING} If this option is present then the existing file is truncated to * a size of 0 bytes. This option is ignored when the file is opened only * for reading.
{@link StandardOpenOption#CREATE_NEW CREATE_NEW} If this option is present then a new file is created, failing if * the file already exists or is a symbolic link. When creating a file the * check for the existence of the file and the creation of the file if it * does not exist is atomic with respect to other file system operations. * This option is ignored when the file is opened only for reading.
{@link StandardOpenOption#CREATE CREATE} If this option is present then an existing file is opened if it * exists, otherwise a new file is created. This option is ignored if the * {@code CREATE_NEW} option is also present or the file is opened only * for reading.
{@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} When this option is present then the implementation makes a * best effort attempt to delete the file when closed by the * {@link SeekableByteChannel#close close} method. If the {@code close} * method is not invoked then a best effort attempt is made to * delete the file when the Java virtual machine terminates.
{@link StandardOpenOption#SPARSE SPARSE} When creating a new file this option is a hint that the * new file will be sparse. This option is ignored when not creating * a new file.
{@link StandardOpenOption#SYNC SYNC} Requires that every update to the file's content or metadata be * written synchronously to the underlying storage device. (see Synchronized I/O file * integrity).
{@link StandardOpenOption#DSYNC DSYNC} Requires that every update to the file's content be written * synchronously to the underlying storage device. (see Synchronized I/O file * integrity).
* *

An implementation may also support additional implementation specific * options. * *

The {@code attrs} parameter is optional {@link FileAttribute * file-attributes} to set atomically when a new file is created. * *

In the case of the default provider, the returned seekable byte channel * is a {@link java.nio.channels.FileChannel}. * *

Usage Examples: *

     *     Path path = ...
     *
     *     // open file for reading
     *     ReadableByteChannel rbc = Files.newByteChannel(path, EnumSet.of(READ)));
     *
     *     // open file for writing to the end of an existing file, creating
     *     // the file if it doesn't already exist
     *     WritableByteChannel wbc = Files.newByteChannel(path, EnumSet.of(CREATE,APPEND));
     *
     *     // create file with initial permissions, opening it for both reading and writing
     *     {@code FileAttribute<> perms = ...}
     *     SeekableByteChannel sbc = Files.newByteChannel(path, EnumSet.of(CREATE_NEW,READ,WRITE), perms);
     * 
* * @param path * the path to the file to open or create * @param options * options specifying how the file is opened * @param attrs * an optional list of file attributes to set atomically when * creating the file * * @return a new seekable byte channel * * @throws IllegalArgumentException * if the set contains an invalid combination of options * @throws UnsupportedOperationException * if an unsupported open option is specified or the array contains * attributes that cannot be set atomically when creating the file * @throws FileAlreadyExistsException * if a file of that name already exists and the {@link * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified * (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the path if the file is * opened for reading. The {@link SecurityManager#checkWrite(String) * checkWrite} method is invoked to check write access to the path * if the file is opened for writing. The {@link * SecurityManager#checkDelete(String) checkDelete} method is * invoked to check delete access if the file is opened with the * {@code DELETE_ON_CLOSE} option. * * @see java.nio.channels.FileChannel#open(Path,Set,FileAttribute[]) */ public static SeekableByteChannel newByteChannel(Path path, Set options, FileAttribute... attrs) throws IOException { return provider(path).newByteChannel(path, options, attrs); } /** * Opens or creates a file, returning a seekable byte channel to access the * file. * *

This method opens or creates a file in exactly the manner specified * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel} * method. * * @param path * the path to the file to open or create * @param options * options specifying how the file is opened * * @return a new seekable byte channel * * @throws IllegalArgumentException * if the set contains an invalid combination of options * @throws UnsupportedOperationException * if an unsupported open option is specified * @throws FileAlreadyExistsException * if a file of that name already exists and the {@link * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified * (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the path if the file is * opened for reading. The {@link SecurityManager#checkWrite(String) * checkWrite} method is invoked to check write access to the path * if the file is opened for writing. The {@link * SecurityManager#checkDelete(String) checkDelete} method is * invoked to check delete access if the file is opened with the * {@code DELETE_ON_CLOSE} option. * * @see java.nio.channels.FileChannel#open(Path,OpenOption[]) */ public static SeekableByteChannel newByteChannel(Path path, OpenOption... options) throws IOException { Set set = new HashSet(options.length); Collections.addAll(set, options); return newByteChannel(path, set); } // -- Directories -- private static class AcceptAllFilter implements DirectoryStream.Filter { private AcceptAllFilter() { } @Override public boolean accept(Path entry) { return true; } static final AcceptAllFilter FILTER = new AcceptAllFilter(); } /** * Opens a directory, returning a {@link DirectoryStream} to iterate over * all entries in the directory. The elements returned by the directory * stream's {@link DirectoryStream#iterator iterator} are of type {@code * Path}, each one representing an entry in the directory. The {@code Path} * objects are obtained as if by {@link Path#resolve(Path) resolving} the * name of the directory entry against {@code dir}. * *

When not using the try-with-resources construct, then directory * stream's {@code close} method should be invoked after iteration is * completed so as to free any resources held for the open directory. * *

When an implementation supports operations on entries in the * directory that execute in a race-free manner then the returned directory * stream is a {@link SecureDirectoryStream}. * * @param dir * the path to the directory * * @return a new and open {@code DirectoryStream} object * * @throws NotDirectoryException * if the file could not otherwise be opened because it is not * a directory (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the directory. */ public static DirectoryStream newDirectoryStream(Path dir) throws IOException { return provider(dir).newDirectoryStream(dir, AcceptAllFilter.FILTER); } /** * Opens a directory, returning a {@link DirectoryStream} to iterate over * the entries in the directory. The elements returned by the directory * stream's {@link DirectoryStream#iterator iterator} are of type {@code * Path}, each one representing an entry in the directory. The {@code Path} * objects are obtained as if by {@link Path#resolve(Path) resolving} the * name of the directory entry against {@code dir}. The entries returned by * the iterator are filtered by matching the {@code String} representation * of their file names against the given globbing pattern. * *

For example, suppose we want to iterate over the files ending with * ".java" in a directory: *

     *     Path dir = ...
     *     try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
     *         :
     *     }
     * 
* *

The globbing pattern is specified by the {@link * FileSystem#getPathMatcher getPathMatcher} method. * *

When not using the try-with-resources construct, then directory * stream's {@code close} method should be invoked after iteration is * completed so as to free any resources held for the open directory. * *

When an implementation supports operations on entries in the * directory that execute in a race-free manner then the returned directory * stream is a {@link SecureDirectoryStream}. * * @param dir * the path to the directory * @param glob * the glob pattern * * @return a new and open {@code DirectoryStream} object * * @throws java.util.regex.PatternSyntaxException * if the pattern is invalid * @throws NotDirectoryException * if the file could not otherwise be opened because it is not * a directory (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the directory. */ public static DirectoryStream newDirectoryStream(Path dir, String glob) throws IOException { // avoid creating a matcher if all entries are required. if (glob.equals("*")) return newDirectoryStream(dir); // create a matcher and return a filter that uses it. FileSystem fs = dir.getFileSystem(); final PathMatcher matcher = fs.getPathMatcher("glob:" + glob); DirectoryStream.Filter filter = new DirectoryStream.Filter() { @Override public boolean accept(Path entry) { return matcher.matches(entry.getFileName()); } }; return fs.provider().newDirectoryStream(dir, filter); } /** * Opens a directory, returning a {@link DirectoryStream} to iterate over * the entries in the directory. The elements returned by the directory * stream's {@link DirectoryStream#iterator iterator} are of type {@code * Path}, each one representing an entry in the directory. The {@code Path} * objects are obtained as if by {@link Path#resolve(Path) resolving} the * name of the directory entry against {@code dir}. The entries returned by * the iterator are filtered by the given {@link DirectoryStream.Filter * filter}. * *

When not using the try-with-resources construct, then directory * stream's {@code close} method should be invoked after iteration is * completed so as to free any resources held for the open directory. * *

Where the filter terminates due to an uncaught error or runtime * exception then it is propagated to the {@link Iterator#hasNext() * hasNext} or {@link Iterator#next() next} method. Where an {@code * IOException} is thrown, it results in the {@code hasNext} or {@code * next} method throwing a {@link DirectoryIteratorException} with the * {@code IOException} as the cause. * *

When an implementation supports operations on entries in the * directory that execute in a race-free manner then the returned directory * stream is a {@link SecureDirectoryStream}. * *

Usage Example: * Suppose we want to iterate over the files in a directory that are * larger than 8K. *

     *     DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
     *         public boolean accept(Path file) throws IOException {
     *             return (Files.size(file) > 8192L);
     *         }
     *     };
     *     Path dir = ...
     *     try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
     *         :
     *     }
     * 
* * @param dir * the path to the directory * @param filter * the directory stream filter * * @return a new and open {@code DirectoryStream} object * * @throws NotDirectoryException * if the file could not otherwise be opened because it is not * a directory (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the directory. */ public static DirectoryStream newDirectoryStream(Path dir, DirectoryStream.Filter filter) throws IOException { return provider(dir).newDirectoryStream(dir, filter); } // -- Creation and deletion -- /** * Creates a new and empty file, failing if the file already exists. The * check for the existence of the file and the creation of the new file if * it does not exist are a single operation that is atomic with respect to * all other filesystem activities that might affect the directory. * *

The {@code attrs} parameter is optional {@link FileAttribute * file-attributes} to set atomically when creating the file. Each attribute * is identified by its {@link FileAttribute#name name}. If more than one * attribute of the same name is included in the array then all but the last * occurrence is ignored. * * @param path * the path to the file to create * @param attrs * an optional list of file attributes to set atomically when * creating the file * * @return the file * * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the file * @throws FileAlreadyExistsException * if a file of that name already exists * (optional specific exception) * @throws IOException * if an I/O error occurs or the parent directory does not exist * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the new file. */ public static Path createFile(Path path, FileAttribute... attrs) throws IOException { EnumSet options = EnumSet.of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE); newByteChannel(path, options, attrs).close(); return path; } /** * Creates a new directory. The check for the existence of the file and the * creation of the directory if it does not exist are a single operation * that is atomic with respect to all other filesystem activities that might * affect the directory. The {@link #createDirectories createDirectories} * method should be used where it is required to create all nonexistent * parent directories first. * *

The {@code attrs} parameter is optional {@link FileAttribute * file-attributes} to set atomically when creating the directory. Each * attribute is identified by its {@link FileAttribute#name name}. If more * than one attribute of the same name is included in the array then all but * the last occurrence is ignored. * * @param dir * the directory to create * @param attrs * an optional list of file attributes to set atomically when * creating the directory * * @return the directory * * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the directory * @throws FileAlreadyExistsException * if a directory could not otherwise be created because a file of * that name already exists (optional specific exception) * @throws IOException * if an I/O error occurs or the parent directory does not exist * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the new directory. */ public static Path createDirectory(Path dir, FileAttribute... attrs) throws IOException { provider(dir).createDirectory(dir, attrs); return dir; } /** * Creates a directory by creating all nonexistent parent directories first. * Unlike the {@link #createDirectory createDirectory} method, an exception * is not thrown if the directory could not be created because it already * exists. * *

The {@code attrs} parameter is optional {@link FileAttribute * file-attributes} to set atomically when creating the nonexistent * directories. Each file attribute is identified by its {@link * FileAttribute#name name}. If more than one attribute of the same name is * included in the array then all but the last occurrence is ignored. * *

If this method fails, then it may do so after creating some, but not * all, of the parent directories. * * @param dir * the directory to create * * @param attrs * an optional list of file attributes to set atomically when * creating the directory * * @return the directory * * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the directory * @throws FileAlreadyExistsException * if {@code dir} exists but is not a directory (optional specific * exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * in the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked prior to attempting to create a directory and * its {@link SecurityManager#checkRead(String) checkRead} is * invoked for each parent directory that is checked. If {@code * dir} is not an absolute path then its {@link Path#toAbsolutePath * toAbsolutePath} may need to be invoked to get its absolute path. * This may invoke the security manager's {@link * SecurityManager#checkPropertyAccess(String) checkPropertyAccess} * method to check access to the system property {@code user.dir} */ public static Path createDirectories(Path dir, FileAttribute... attrs) throws IOException { // attempt to create the directory try { createAndCheckIsDirectory(dir, attrs); return dir; } catch (FileAlreadyExistsException x) { // file exists and is not a directory throw x; } catch (IOException x) { // parent may not exist or other reason } SecurityException se = null; try { dir = dir.toAbsolutePath(); } catch (SecurityException x) { // don't have permission to get absolute path se = x; } // find a decendent that exists Path parent = dir.getParent(); while (parent != null) { try { provider(parent).checkAccess(parent); break; } catch (NoSuchFileException x) { // does not exist } parent = parent.getParent(); } if (parent == null) { // unable to find existing parent if (se != null) throw se; throw new IOException("Root directory does not exist"); } // create directories Path child = parent; for (Path name: parent.relativize(dir)) { child = child.resolve(name); createAndCheckIsDirectory(child, attrs); } return dir; } /** * Used by createDirectories to attempt to create a directory. A no-op * if the directory already exists. */ private static void createAndCheckIsDirectory(Path dir, FileAttribute... attrs) throws IOException { try { createDirectory(dir, attrs); } catch (FileAlreadyExistsException x) { if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS)) throw x; } } /** * Creates a new empty file in the specified directory, using the given * prefix and suffix strings to generate its name. The resulting * {@code Path} is associated with the same {@code FileSystem} as the given * directory. * *

The details as to how the name of the file is constructed is * implementation dependent and therefore not specified. Where possible * the {@code prefix} and {@code suffix} are used to construct candidate * names in the same manner as the {@link * java.io.File#createTempFile(String,String,File)} method. * *

As with the {@code File.createTempFile} methods, this method is only * part of a temporary-file facility. Where used as a work files, * the resulting file may be opened using the {@link * StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the * file is deleted when the appropriate {@code close} method is invoked. * Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the * {@link java.io.File#deleteOnExit} mechanism may be used to delete the * file automatically. * *

The {@code attrs} parameter is optional {@link FileAttribute * file-attributes} to set atomically when creating the file. Each attribute * is identified by its {@link FileAttribute#name name}. If more than one * attribute of the same name is included in the array then all but the last * occurrence is ignored. When no file attributes are specified, then the * resulting file may have more restrictive access permissions to files * created by the {@link java.io.File#createTempFile(String,String,File)} * method. * * @param dir * the path to directory in which to create the file * @param prefix * the prefix string to be used in generating the file's name; * may be {@code null} * @param suffix * the suffix string to be used in generating the file's name; * may be {@code null}, in which case "{@code .tmp}" is used * @param attrs * an optional list of file attributes to set atomically when * creating the file * * @return the path to the newly created file that did not exist before * this method was invoked * * @throws IllegalArgumentException * if the prefix or suffix parameters cannot be used to generate * a candidate file name * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the directory * @throws IOException * if an I/O error occurs or {@code dir} does not exist * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. */ public static Path createTempFile(Path dir, String prefix, String suffix, FileAttribute... attrs) throws IOException { return TempFileHelper.createTempFile(Objects.requireNonNull(dir), prefix, suffix, attrs); } /** * Creates an empty file in the default temporary-file directory, using * the given prefix and suffix to generate its name. The resulting {@code * Path} is associated with the default {@code FileSystem}. * *

This method works in exactly the manner specified by the * {@link #createTempFile(Path,String,String,FileAttribute[])} method for * the case that the {@code dir} parameter is the temporary-file directory. * * @param prefix * the prefix string to be used in generating the file's name; * may be {@code null} * @param suffix * the suffix string to be used in generating the file's name; * may be {@code null}, in which case "{@code .tmp}" is used * @param attrs * an optional list of file attributes to set atomically when * creating the file * * @return the path to the newly created file that did not exist before * this method was invoked * * @throws IllegalArgumentException * if the prefix or suffix parameters cannot be used to generate * a candidate file name * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the directory * @throws IOException * if an I/O error occurs or the temporary-file directory does not * exist * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. */ public static Path createTempFile(String prefix, String suffix, FileAttribute... attrs) throws IOException { return TempFileHelper.createTempFile(null, prefix, suffix, attrs); } /** * Creates a new directory in the specified directory, using the given * prefix to generate its name. The resulting {@code Path} is associated * with the same {@code FileSystem} as the given directory. * *

The details as to how the name of the directory is constructed is * implementation dependent and therefore not specified. Where possible * the {@code prefix} is used to construct candidate names. * *

As with the {@code createTempFile} methods, this method is only * part of a temporary-file facility. A {@link Runtime#addShutdownHook * shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be * used to delete the directory automatically. * *

The {@code attrs} parameter is optional {@link FileAttribute * file-attributes} to set atomically when creating the directory. Each * attribute is identified by its {@link FileAttribute#name name}. If more * than one attribute of the same name is included in the array then all but * the last occurrence is ignored. * * @param dir * the path to directory in which to create the directory * @param prefix * the prefix string to be used in generating the directory's name; * may be {@code null} * @param attrs * an optional list of file attributes to set atomically when * creating the directory * * @return the path to the newly created directory that did not exist before * this method was invoked * * @throws IllegalArgumentException * if the prefix cannot be used to generate a candidate directory name * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the directory * @throws IOException * if an I/O error occurs or {@code dir} does not exist * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access when creating the * directory. */ public static Path createTempDirectory(Path dir, String prefix, FileAttribute... attrs) throws IOException { return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir), prefix, attrs); } /** * Creates a new directory in the default temporary-file directory, using * the given prefix to generate its name. The resulting {@code Path} is * associated with the default {@code FileSystem}. * *

This method works in exactly the manner specified by {@link * #createTempDirectory(Path,String,FileAttribute[])} method for the case * that the {@code dir} parameter is the temporary-file directory. * * @param prefix * the prefix string to be used in generating the directory's name; * may be {@code null} * @param attrs * an optional list of file attributes to set atomically when * creating the directory * * @return the path to the newly created directory that did not exist before * this method was invoked * * @throws IllegalArgumentException * if the prefix cannot be used to generate a candidate directory name * @throws UnsupportedOperationException * if the array contains an attribute that cannot be set atomically * when creating the directory * @throws IOException * if an I/O error occurs or the temporary-file directory does not * exist * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access when creating the * directory. */ public static Path createTempDirectory(String prefix, FileAttribute... attrs) throws IOException { return TempFileHelper.createTempDirectory(null, prefix, attrs); } /** * Creates a symbolic link to a target (optional operation). * *

The {@code target} parameter is the target of the link. It may be an * {@link Path#isAbsolute absolute} or relative path and may not exist. When * the target is a relative path then file system operations on the resulting * link are relative to the path of the link. * *

The {@code attrs} parameter is optional {@link FileAttribute * attributes} to set atomically when creating the link. Each attribute is * identified by its {@link FileAttribute#name name}. If more than one attribute * of the same name is included in the array then all but the last occurrence * is ignored. * *

Where symbolic links are supported, but the underlying {@link FileStore} * does not support symbolic links, then this may fail with an {@link * IOException}. Additionally, some operating systems may require that the * Java virtual machine be started with implementation specific privileges to * create symbolic links, in which case this method may throw {@code IOException}. * * @param link * the path of the symbolic link to create * @param target * the target of the symbolic link * @param attrs * the array of attributes to set atomically when creating the * symbolic link * * @return the path to the symbolic link * * @throws UnsupportedOperationException * if the implementation does not support symbolic links or the * array contains an attribute that cannot be set atomically when * creating the symbolic link * @throws FileAlreadyExistsException * if a file with the name already exists (optional specific * exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager * is installed, it denies {@link LinkPermission}("symbolic") * or its {@link SecurityManager#checkWrite(String) checkWrite} * method denies write access to the path of the symbolic link. */ public static Path createSymbolicLink(Path link, Path target, FileAttribute... attrs) throws IOException { provider(link).createSymbolicLink(link, target, attrs); return link; } /** * Creates a new link (directory entry) for an existing file (optional * operation). * *

The {@code link} parameter locates the directory entry to create. * The {@code existing} parameter is the path to an existing file. This * method creates a new directory entry for the file so that it can be * accessed using {@code link} as the path. On some file systems this is * known as creating a "hard link". Whether the file attributes are * maintained for the file or for each directory entry is file system * specific and therefore not specified. Typically, a file system requires * that all links (directory entries) for a file be on the same file system. * Furthermore, on some platforms, the Java virtual machine may require to * be started with implementation specific privileges to create hard links * or to create links to directories. * * @param link * the link (directory entry) to create * @param existing * a path to an existing file * * @return the path to the link (directory entry) * * @throws UnsupportedOperationException * if the implementation does not support adding an existing file * to a directory * @throws FileAlreadyExistsException * if the entry could not otherwise be created because a file of * that name already exists (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager * is installed, it denies {@link LinkPermission}("hard") * or its {@link SecurityManager#checkWrite(String) checkWrite} * method denies write access to either the link or the * existing file. */ public static Path createLink(Path link, Path existing) throws IOException { provider(link).createLink(link, existing); return link; } /** * Deletes a file. * *

An implementation may require to examine the file to determine if the * file is a directory. Consequently this method may not be atomic with respect * to other file system operations. If the file is a symbolic link then the * symbolic link itself, not the final target of the link, is deleted. * *

If the file is a directory then the directory must be empty. In some * implementations a directory has entries for special files or links that * are created when the directory is created. In such implementations a * directory is considered empty when only the special entries exist. * This method can be used with the {@link #walkFileTree walkFileTree} * method to delete a directory and all entries in the directory, or an * entire file-tree where required. * *

On some operating systems it may not be possible to remove a file when * it is open and in use by this Java virtual machine or other programs. * * @param path * the path to the file to delete * * @throws NoSuchFileException * if the file does not exist (optional specific exception) * @throws DirectoryNotEmptyException * if the file is a directory and could not otherwise be deleted * because the directory is not empty (optional specific * exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkDelete(String)} method * is invoked to check delete access to the file */ public static void delete(Path path) throws IOException { provider(path).delete(path); } /** * Deletes a file if it exists. * *

As with the {@link #delete(Path) delete(Path)} method, an * implementation may need to examine the file to determine if the file is a * directory. Consequently this method may not be atomic with respect to * other file system operations. If the file is a symbolic link, then the * symbolic link itself, not the final target of the link, is deleted. * *

If the file is a directory then the directory must be empty. In some * implementations a directory has entries for special files or links that * are created when the directory is created. In such implementations a * directory is considered empty when only the special entries exist. * *

On some operating systems it may not be possible to remove a file when * it is open and in use by this Java virtual machine or other programs. * * @param path * the path to the file to delete * * @return {@code true} if the file was deleted by this method; {@code * false} if the file could not be deleted because it did not * exist * * @throws DirectoryNotEmptyException * if the file is a directory and could not otherwise be deleted * because the directory is not empty (optional specific * exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkDelete(String)} method * is invoked to check delete access to the file. */ public static boolean deleteIfExists(Path path) throws IOException { return provider(path).deleteIfExists(path); } // -- Copying and moving files -- /** * Copy a file to a target file. * *

This method copies a file to the target file with the {@code * options} parameter specifying how the copy is performed. By default, the * copy fails if the target file already exists or is a symbolic link, * except if the source and target are the {@link #isSameFile same} file, in * which case the method completes without copying the file. File attributes * are not required to be copied to the target file. If symbolic links are * supported, and the file is a symbolic link, then the final target of the * link is copied. If the file is a directory then it creates an empty * directory in the target location (entries in the directory are not * copied). This method can be used with the {@link #walkFileTree * walkFileTree} method to copy a directory and all entries in the directory, * or an entire file-tree where required. * *

The {@code options} parameter may include any of the following: * * * * * * * * * * * * * * * *
Option Description
{@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} If the target file exists, then the target file is replaced if it * is not a non-empty directory. If the target file exists and is a * symbolic link, then the symbolic link itself, not the target of * the link, is replaced.
{@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES} Attempts to copy the file attributes associated with this file to * the target file. The exact file attributes that are copied is platform * and file system dependent and therefore unspecified. Minimally, the * {@link BasicFileAttributes#lastModifiedTime last-modified-time} is * copied to the target file if supported by both the source and target * file store. Copying of file timestamps may result in precision * loss.
{@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} Symbolic links are not followed. If the file is a symbolic link, * then the symbolic link itself, not the target of the link, is copied. * It is implementation specific if file attributes can be copied to the * new link. In other words, the {@code COPY_ATTRIBUTES} option may be * ignored when copying a symbolic link.
* *

An implementation of this interface may support additional * implementation specific options. * *

Copying a file is not an atomic operation. If an {@link IOException} * is thrown then it possible that the target file is incomplete or some of * its file attributes have not been copied from the source file. When the * {@code REPLACE_EXISTING} option is specified and the target file exists, * then the target file is replaced. The check for the existence of the file * and the creation of the new file may not be atomic with respect to other * file system activities. * *

Usage Example: * Suppose we want to copy a file into a directory, giving it the same file * name as the source file: *

     *     Path source = ...
     *     Path newdir = ...
     *     Files.copy(source, newdir.resolve(source.getFileName());
     * 
* * @param source * the path to the file to copy * @param target * the path to the target file (may be associated with a different * provider to the source path) * @param options * options specifying how the copy should be done * * @return the path to the target file * * @throws UnsupportedOperationException * if the array contains a copy option that is not supported * @throws FileAlreadyExistsException * if the target file exists but cannot be replaced because the * {@code REPLACE_EXISTING} option is not specified (optional * specific exception) * @throws DirectoryNotEmptyException * the {@code REPLACE_EXISTING} option is specified but the file * cannot be replaced because it is a non-empty directory * (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the source file, the * {@link SecurityManager#checkWrite(String) checkWrite} is invoked * to check write access to the target file. If a symbolic link is * copied the security manager is invoked to check {@link * LinkPermission}{@code ("symbolic")}. */ public static Path copy(Path source, Path target, CopyOption... options) throws IOException { FileSystemProvider provider = provider(source); if (provider(target) == provider) { // same provider provider.copy(source, target, options); } else { // different providers CopyMoveHelper.copyToForeignTarget(source, target, options); } return target; } /** * Move or rename a file to a target file. * *

By default, this method attempts to move the file to the target * file, failing if the target file exists except if the source and * target are the {@link #isSameFile same} file, in which case this method * has no effect. If the file is a symbolic link then the symbolic link * itself, not the target of the link, is moved. This method may be * invoked to move an empty directory. In some implementations a directory * has entries for special files or links that are created when the * directory is created. In such implementations a directory is considered * empty when only the special entries exist. When invoked to move a * directory that is not empty then the directory is moved if it does not * require moving the entries in the directory. For example, renaming a * directory on the same {@link FileStore} will usually not require moving * the entries in the directory. When moving a directory requires that its * entries be moved then this method fails (by throwing an {@code * IOException}). To move a file tree may involve copying rather * than moving directories and this can be done using the {@link * #copy copy} method in conjunction with the {@link * #walkFileTree Files.walkFileTree} utility method. * *

The {@code options} parameter may include any of the following: * * * * * * * * * * *
Option Description
{@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} If the target file exists, then the target file is replaced if it * is not a non-empty directory. If the target file exists and is a * symbolic link, then the symbolic link itself, not the target of * the link, is replaced.
{@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} The move is performed as an atomic file system operation and all * other options are ignored. If the target file exists then it is * implementation specific if the existing file is replaced or this method * fails by throwing an {@link IOException}. If the move cannot be * performed as an atomic file system operation then {@link * AtomicMoveNotSupportedException} is thrown. This can arise, for * example, when the target location is on a different {@code FileStore} * and would require that the file be copied, or target location is * associated with a different provider to this object.
* *

An implementation of this interface may support additional * implementation specific options. * *

Where the move requires that the file be copied then the {@link * BasicFileAttributes#lastModifiedTime last-modified-time} is copied to the * new file. An implementation may also attempt to copy other file * attributes but is not required to fail if the file attributes cannot be * copied. When the move is performed as a non-atomic operation, and a {@code * IOException} is thrown, then the state of the files is not defined. The * original file and the target file may both exist, the target file may be * incomplete or some of its file attributes may not been copied from the * original file. * *

Usage Examples: * Suppose we want to rename a file to "newname", keeping the file in the * same directory: *

     *     Path source = ...
     *     Files.move(source, source.resolveSibling("newname"));
     * 
* Alternatively, suppose we want to move a file to new directory, keeping * the same file name, and replacing any existing file of that name in the * directory: *
     *     Path source = ...
     *     Path newdir = ...
     *     Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
     * 
* * @param source * the path to the file to move * @param target * the path to the target file (may be associated with a different * provider to the source path) * @param options * options specifying how the move should be done * * @return the path to the target file * * @throws UnsupportedOperationException * if the array contains a copy option that is not supported * @throws FileAlreadyExistsException * if the target file exists but cannot be replaced because the * {@code REPLACE_EXISTING} option is not specified (optional * specific exception) * @throws DirectoryNotEmptyException * the {@code REPLACE_EXISTING} option is specified but the file * cannot be replaced because it is a non-empty directory * (optional specific exception) * @throws AtomicMoveNotSupportedException * if the options array contains the {@code ATOMIC_MOVE} option but * the file cannot be moved as an atomic file system operation. * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to both the source and * target file. */ public static Path move(Path source, Path target, CopyOption... options) throws IOException { FileSystemProvider provider = provider(source); if (provider(target) == provider) { // same provider provider.move(source, target, options); } else { // different providers CopyMoveHelper.moveToForeignTarget(source, target, options); } return target; } // -- Miscellenous -- /** * Reads the target of a symbolic link (optional operation). * *

If the file system supports symbolic * links then this method is used to read the target of the link, failing * if the file is not a symbolic link. The target of the link need not exist. * The returned {@code Path} object will be associated with the same file * system as {@code link}. * * @param link * the path to the symbolic link * * @return a {@code Path} object representing the target of the link * * @throws UnsupportedOperationException * if the implementation does not support symbolic links * @throws NotLinkException * if the target could otherwise not be read because the file * is not a symbolic link (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager * is installed, it checks that {@code FilePermission} has been * granted with the "{@code readlink}" action to read the link. */ public static Path readSymbolicLink(Path link) throws IOException { return provider(link).readSymbolicLink(link); } /** * Returns the {@link FileStore} representing the file store where a file * is located. * *

Once a reference to the {@code FileStore} is obtained it is * implementation specific if operations on the returned {@code FileStore}, * or {@link FileStoreAttributeView} objects obtained from it, continue * to depend on the existence of the file. In particular the behavior is not * defined for the case that the file is deleted or moved to a different * file store. * * @param path * the path to the file * * @return the file store where the file is stored * * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file, and in * addition it checks {@link RuntimePermission} * ("getFileStoreAttributes") */ public static FileStore getFileStore(Path path) throws IOException { return provider(path).getFileStore(path); } /** * Tests if two paths locate the same file. * *

If both {@code Path} objects are {@link Path#equals(Object) equal} * then this method returns {@code true} without checking if the file exists. * If the two {@code Path} objects are associated with different providers * then this method returns {@code false}. Otherwise, this method checks if * both {@code Path} objects locate the same file, and depending on the * implementation, may require to open or access both files. * *

If the file system and files remain static, then this method implements * an equivalence relation for non-null {@code Paths}. *

* * @param path * one path to the file * @param path2 * the other path * * @return {@code true} if, and only if, the two paths locate the same file * * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to both files. * * @see java.nio.file.attribute.BasicFileAttributes#fileKey */ public static boolean isSameFile(Path path, Path path2) throws IOException { return provider(path).isSameFile(path, path2); } /** * Tells whether or not a file is considered hidden. The exact * definition of hidden is platform or provider dependent. On UNIX for * example a file is considered to be hidden if its name begins with a * period character ('.'). On Windows a file is considered hidden if it * isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden} * attribute is set. * *

Depending on the implementation this method may require to access * the file system to determine if the file is considered hidden. * * @param path * the path to the file to test * * @return {@code true} if the file is considered hidden * * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. */ public static boolean isHidden(Path path) throws IOException { return provider(path).isHidden(path); } // lazy loading of default and installed file type detectors private static class FileTypeDetectors{ static final FileTypeDetector defaultFileTypeDetector = createDefaultFileTypeDetector(); static final List installeDetectors = loadInstalledDetectors(); // creates the default file type detector private static FileTypeDetector createDefaultFileTypeDetector() { return AccessController .doPrivileged(new PrivilegedAction() { @Override public FileTypeDetector run() { return sun.nio.fs.DefaultFileTypeDetector.create(); }}); } // loads all installed file type detectors private static List loadInstalledDetectors() { return AccessController .doPrivileged(new PrivilegedAction>() { @Override public List run() { List list = new ArrayList<>(); ServiceLoader loader = ServiceLoader .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader()); for (FileTypeDetector detector: loader) { list.add(detector); } return list; }}); } } /** * Probes the content type of a file. * *

This method uses the installed {@link FileTypeDetector} implementations * to probe the given file to determine its content type. Each file type * detector's {@link FileTypeDetector#probeContentType probeContentType} is * invoked, in turn, to probe the file type. If the file is recognized then * the content type is returned. If the file is not recognized by any of the * installed file type detectors then a system-default file type detector is * invoked to guess the content type. * *

A given invocation of the Java virtual machine maintains a system-wide * list of file type detectors. Installed file type detectors are loaded * using the service-provider loading facility defined by the {@link ServiceLoader} * class. Installed file type detectors are loaded using the system class * loader. If the system class loader cannot be found then the extension class * loader is used; If the extension class loader cannot be found then the * bootstrap class loader is used. File type detectors are typically installed * by placing them in a JAR file on the application class path or in the * extension directory, the JAR file contains a provider-configuration file * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory * {@code META-INF/services}, and the file lists one or more fully-qualified * names of concrete subclass of {@code FileTypeDetector } that have a zero * argument constructor. If the process of locating or instantiating the * installed file type detectors fails then an unspecified error is thrown. * The ordering that installed providers are located is implementation * specific. * *

The return value of this method is the string form of the value of a * Multipurpose Internet Mail Extension (MIME) content type as * defined by RFC 2045: * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet * Message Bodies. The string is guaranteed to be parsable according * to the grammar in the RFC. * * @param path * the path to the file to probe * * @return The content type of the file, or {@code null} if the content * type cannot be determined * * @throws IOException * if an I/O error occurs * @throws SecurityException * If a security manager is installed and it denies an unspecified * permission required by a file type detector implementation. */ public static String probeContentType(Path path) throws IOException { // try installed file type detectors for (FileTypeDetector detector: FileTypeDetectors.installeDetectors) { String result = detector.probeContentType(path); if (result != null) return result; } // fallback to default return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path); } // -- File Attributes -- /** * Returns a file attribute view of a given type. * *

A file attribute view provides a read-only or updatable view of a * set of file attributes. This method is intended to be used where the file * attribute view defines type-safe methods to read or update the file * attributes. The {@code type} parameter is the type of the attribute view * required and the method returns an instance of that type if supported. * The {@link BasicFileAttributeView} type supports access to the basic * attributes of a file. Invoking this method to select a file attribute * view of that type will always return an instance of that class. * *

The {@code options} array may be used to indicate how symbolic links * are handled by the resulting file attribute view for the case that the * file is a symbolic link. By default, symbolic links are followed. If the * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then * symbolic links are not followed. This option is ignored by implementations * that do not support symbolic links. * *

Usage Example: * Suppose we want read or set a file's ACL, if supported: *

     *     Path path = ...
     *     AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
     *     if (view != null) {
     *         List<AclEntry> acl = view.getAcl();
     *         :
     *     }
     * 
* * * @param path * the path to the file * @param type * the {@code Class} object corresponding to the file attribute view * @param options * options indicating how symbolic links are handled * * @return a file attribute view of the specified type, or {@code null} if * the attribute view type is not available */ public static V getFileAttributeView(Path path, Class type, LinkOption... options) { return provider(path).getFileAttributeView(path, type, options); } /** * Reads a file's attributes as a bulk operation. * *

The {@code type} parameter is the type of the attributes required * and this method returns an instance of that type if supported. All * implementations support a basic set of file attributes and so invoking * this method with a {@code type} parameter of {@code * BasicFileAttributes.class} will not throw {@code * UnsupportedOperationException}. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

It is implementation specific if all file attributes are read as an * atomic operation with respect to other file system operations. * *

Usage Example: * Suppose we want to read a file's attributes in bulk: *

     *    Path path = ...
     *    BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
     * 
* Alternatively, suppose we want to read file's POSIX attributes without * following symbolic links: *
     *    PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
     * 
* * @param path * the path to the file * @param type * the {@code Class} of the file attributes required * to read * @param options * options indicating how symbolic links are handled * * @return the file attributes * * @throws UnsupportedOperationException * if an attributes of the given type are not supported * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. If this * method is invoked to read security sensitive attributes then the * security manager may be invoke to check for additional permissions. */ public static A readAttributes(Path path, Class type, LinkOption... options) throws IOException { return provider(path).readAttributes(path, type, options); } /** * Sets the value of a file attribute. * *

The {@code attribute} parameter identifies the attribute to be set * and takes the form: *

* [view-name:]attribute-name *
* where square brackets [...] delineate an optional component and the * character {@code ':'} stands for itself. * *

view-name is the {@link FileAttributeView#name name} of a {@link * FileAttributeView} that identifies a set of file attributes. If not * specified then it defaults to {@code "basic"}, the name of the file * attribute view that identifies the basic set of file attributes common to * many file systems. attribute-name is the name of the attribute * within the set. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

Usage Example: * Suppose we want to set the DOS "hidden" attribute: *

     *    Path path = ...
     *    Files.setAttribute(path, "dos:hidden", true);
     * 
* * @param path * the path to the file * @param attribute * the attribute to set * @param value * the attribute value * @param options * options indicating how symbolic links are handled * * @return the {@code path} parameter * * @throws UnsupportedOperationException * if the attribute view is not available * @throws IllegalArgumentException * if the attribute name is not specified, or is not recognized, or * the attribute value is of the correct type but has an * inappropriate value * @throws ClassCastException * if the attribute value is not of the expected type or is a * collection containing elements that are not of the expected * type * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkWrite(String) checkWrite} * method denies write access to the file. If this method is invoked * to set security sensitive attributes then the security manager * may be invoked to check for additional permissions. */ public static Path setAttribute(Path path, String attribute, Object value, LinkOption... options) throws IOException { provider(path).setAttribute(path, attribute, value, options); return path; } /** * Reads the value of a file attribute. * *

The {@code attribute} parameter identifies the attribute to be read * and takes the form: *

* [view-name:]attribute-name *
* where square brackets [...] delineate an optional component and the * character {@code ':'} stands for itself. * *

view-name is the {@link FileAttributeView#name name} of a {@link * FileAttributeView} that identifies a set of file attributes. If not * specified then it defaults to {@code "basic"}, the name of the file * attribute view that identifies the basic set of file attributes common to * many file systems. attribute-name is the name of the attribute. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

Usage Example: * Suppose we require the user ID of the file owner on a system that * supports a "{@code unix}" view: *

     *    Path path = ...
     *    int uid = (Integer)Files.getAttribute(path, "unix:uid");
     * 
* * @param path * the path to the file * @param attribute * the attribute to read * @param options * options indicating how symbolic links are handled * * @return the attribute value * * @throws UnsupportedOperationException * if the attribute view is not available * @throws IllegalArgumentException * if the attribute name is not specified or is not recognized * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. If this method is invoked * to read security sensitive attributes then the security manager * may be invoked to check for additional permissions. */ public static Object getAttribute(Path path, String attribute, LinkOption... options) throws IOException { // only one attribute should be read if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0) throw new IllegalArgumentException(attribute); Map map = readAttributes(path, attribute, options); assert map.size() == 1; String name; int pos = attribute.indexOf(':'); if (pos == -1) { name = attribute; } else { name = (pos == attribute.length()) ? "" : attribute.substring(pos+1); } return map.get(name); } /** * Reads a set of file attributes as a bulk operation. * *

The {@code attributes} parameter identifies the attributes to be read * and takes the form: *

* [view-name:]attribute-list *
* where square brackets [...] delineate an optional component and the * character {@code ':'} stands for itself. * *

view-name is the {@link FileAttributeView#name name} of a {@link * FileAttributeView} that identifies a set of file attributes. If not * specified then it defaults to {@code "basic"}, the name of the file * attribute view that identifies the basic set of file attributes common to * many file systems. * *

The attribute-list component is a comma separated list of * zero or more names of attributes to read. If the list contains the value * {@code "*"} then all attributes are read. Attributes that are not supported * are ignored and will not be present in the returned map. It is * implementation specific if all attributes are read as an atomic operation * with respect to other file system operations. * *

The following examples demonstrate possible values for the {@code * attributes} parameter: * *

* * * * * * * * * * * * * * * * * *
{@code "*"} Read all {@link BasicFileAttributes basic-file-attributes}.
{@code "size,lastModifiedTime,lastAccessTime"} Reads the file size, last modified time, and last access time * attributes.
{@code "posix:*"} Read all {@link PosixFileAttributes POSIX-file-attributes}.
{@code "posix:permissions,owner,size"} Reads the POSX file permissions, owner, and file size.
*
* *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * * @param path * the path to the file * @param attributes * the attributes to read * @param options * options indicating how symbolic links are handled * * @return a map of the attributes returned; The map's keys are the * attribute names, its values are the attribute values * * @throws UnsupportedOperationException * if the attribute view is not available * @throws IllegalArgumentException * if no attributes are specified or an unrecognized attributes is * specified * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. If this method is invoked * to read security sensitive attributes then the security manager * may be invoke to check for additional permissions. */ public static Map readAttributes(Path path, String attributes, LinkOption... options) throws IOException { return provider(path).readAttributes(path, attributes, options); } /** * Returns a file's POSIX file permissions. * *

The {@code path} parameter is associated with a {@code FileSystem} * that supports the {@link PosixFileAttributeView}. This attribute view * provides access to file attributes commonly associated with files on file * systems used by operating systems that implement the Portable Operating * System Interface (POSIX) family of standards. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * * @param path * the path to the file * @param options * options indicating how symbolic links are handled * * @return the file permissions * * @throws UnsupportedOperationException * if the associated file system does not support the {@code * PosixFileAttributeView} * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, a security manager is * installed, and it denies {@link RuntimePermission}("accessUserInformation") * or its {@link SecurityManager#checkRead(String) checkRead} method * denies read access to the file. */ public static Set getPosixFilePermissions(Path path, LinkOption... options) throws IOException { return readAttributes(path, PosixFileAttributes.class, options).permissions(); } /** * Sets a file's POSIX permissions. * *

The {@code path} parameter is associated with a {@code FileSystem} * that supports the {@link PosixFileAttributeView}. This attribute view * provides access to file attributes commonly associated with files on file * systems used by operating systems that implement the Portable Operating * System Interface (POSIX) family of standards. * * @param path * A file reference that locates the file * @param perms * The new set of permissions * * @throws UnsupportedOperationException * if the associated file system does not support the {@code * PosixFileAttributeView} * @throws ClassCastException * if the sets contains elements that are not of type {@code * PosixFilePermission} * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, it denies {@link RuntimePermission}("accessUserInformation") * or its {@link SecurityManager#checkWrite(String) checkWrite} * method denies write access to the file. */ public static Path setPosixFilePermissions(Path path, Set perms) throws IOException { PosixFileAttributeView view = getFileAttributeView(path, PosixFileAttributeView.class); if (view == null) throw new UnsupportedOperationException(); view.setPermissions(perms); return path; } /** * Returns the owner of a file. * *

The {@code path} parameter is associated with a file system that * supports {@link FileOwnerAttributeView}. This file attribute view provides * access to a file attribute that is the owner of the file. * * @param path * A file reference that locates the file * @param options * options indicating how symbolic links are handled * * @return A user principal representing the owner of the file * * @throws UnsupportedOperationException * if the associated file system does not support the {@code * FileOwnerAttributeView} * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, it denies {@link RuntimePermission}("accessUserInformation") * or its {@link SecurityManager#checkRead(String) checkRead} method * denies read access to the file. */ public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException { FileOwnerAttributeView view = getFileAttributeView(path, FileOwnerAttributeView.class, options); if (view == null) throw new UnsupportedOperationException(); return view.getOwner(); } /** * Updates the file owner. * *

The {@code path} parameter is associated with a file system that * supports {@link FileOwnerAttributeView}. This file attribute view provides * access to a file attribute that is the owner of the file. * *

Usage Example: * Suppose we want to make "joe" the owner of a file: *

     *     Path path = ...
     *     UserPrincipalLookupService lookupService =
     *         provider(path).getUserPrincipalLookupService();
     *     UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
     *     Files.setOwner(path, joe);
     * 
* * @param path * A file reference that locates the file * @param owner * The new file owner * * @throws UnsupportedOperationException * if the associated file system does not support the {@code * FileOwnerAttributeView} * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, it denies {@link RuntimePermission}("accessUserInformation") * or its {@link SecurityManager#checkWrite(String) checkWrite} * method denies write access to the file. * * @see FileSystem#getUserPrincipalLookupService * @see java.nio.file.attribute.UserPrincipalLookupService */ public static Path setOwner(Path path, UserPrincipal owner) throws IOException { FileOwnerAttributeView view = getFileAttributeView(path, FileOwnerAttributeView.class); if (view == null) throw new UnsupportedOperationException(); view.setOwner(owner); return path; } /** * Tests whether a file is a symbolic link. * *

Where is it required to distinguish an I/O exception from the case * that the file is not a symbolic link then the file attributes can be * read with the {@link #readAttributes(Path,Class,LinkOption[]) * readAttributes} method and the file type tested with the {@link * BasicFileAttributes#isSymbolicLink} method. * * @return {@code true} if the file is a symbolic link; {@code false} if * the file does not exist, is not a symbolic link, or it cannot * be determined if the file is a symbolic link or not. * * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. */ public static boolean isSymbolicLink(Path path) { try { return readAttributes(path, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS).isSymbolicLink(); } catch (IOException ioe) { return false; } } /** * Tests whether a file is a directory. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

Where is it required to distinguish an I/O exception from the case * that the file is not a directory then the file attributes can be * read with the {@link #readAttributes(Path,Class,LinkOption[]) * readAttributes} method and the file type tested with the {@link * BasicFileAttributes#isDirectory} method. * * @param path * the path to the file to test * @param options * options indicating how symbolic links are handled * * @return {@code true} if the file is a directory; {@code false} if * the file does not exist, is not a directory, or it cannot * be determined if the file is a directory or not. * * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. */ public static boolean isDirectory(Path path, LinkOption... options) { try { return readAttributes(path, BasicFileAttributes.class, options).isDirectory(); } catch (IOException ioe) { return false; } } /** * Tests whether a file is a regular file with opaque content. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

Where is it required to distinguish an I/O exception from the case * that the file is not a regular file then the file attributes can be * read with the {@link #readAttributes(Path,Class,LinkOption[]) * readAttributes} method and the file type tested with the {@link * BasicFileAttributes#isRegularFile} method. * * @param path * the path to the file * @param options * options indicating how symbolic links are handled * * @return {@code true} if the file is a regular file; {@code false} if * the file does not exist, is not a regular file, or it * cannot be determined if the file is a regular file or not. * * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. */ public static boolean isRegularFile(Path path, LinkOption... options) { try { return readAttributes(path, BasicFileAttributes.class, options).isRegularFile(); } catch (IOException ioe) { return false; } } /** * Returns a file's last modified time. * *

The {@code options} array may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed and the file attribute of the final target * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * * @param path * the path to the file * @param options * options indicating how symbolic links are handled * * @return a {@code FileTime} representing the time the file was last * modified, or an implementation specific default when a time * stamp to indicate the time of last modification is not supported * by the file system * * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. * * @see BasicFileAttributes#lastModifiedTime */ public static FileTime getLastModifiedTime(Path path, LinkOption... options) throws IOException { return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime(); } /** * Updates a file's last modified time attribute. The file time is converted * to the epoch and precision supported by the file system. Converting from * finer to coarser granularities result in precision loss. The behavior of * this method when attempting to set the last modified time when it is not * supported by the file system or is outside the range supported by the * underlying file store is not defined. It may or not fail by throwing an * {@code IOException}. * *

Usage Example: * Suppose we want to set the last modified time to the current time: *

     *    Path path = ...
     *    FileTime now = FileTime.fromMillis(System.currentTimeMillis());
     *    Files.setLastModifiedTime(path, now);
     * 
* * @param path * the path to the file * @param time * the new last modified time * * @return the file * * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, the security manager's {@link * SecurityManager#checkWrite(String) checkWrite} method is invoked * to check write access to file * * @see BasicFileAttributeView#setTimes */ public static Path setLastModifiedTime(Path path, FileTime time) throws IOException { getFileAttributeView(path, BasicFileAttributeView.class) .setTimes(time, null, null); return path; } /** * Returns the size of a file (in bytes). The size may differ from the * actual size on the file system due to compression, support for sparse * files, or other reasons. The size of files that are not {@link * #isRegularFile regular} files is implementation specific and * therefore unspecified. * * @param path * the path to the file * * @return the file size, in bytes * * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, its {@link SecurityManager#checkRead(String) checkRead} * method denies read access to the file. * * @see BasicFileAttributes#size */ public static long size(Path path) throws IOException { return readAttributes(path, BasicFileAttributes.class).size(); } // -- Accessibility -- /** * Returns {@code false} if NOFOLLOW_LINKS is present. */ private static boolean followLinks(LinkOption... options) { boolean followLinks = true; for (LinkOption opt: options) { if (opt == LinkOption.NOFOLLOW_LINKS) { followLinks = false; continue; } if (opt == null) throw new NullPointerException(); throw new AssertionError("Should not get here"); } return followLinks; } /** * Tests whether a file exists. * *

The {@code options} parameter may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

Note that the result of this method is immediately outdated. If this * method indicates the file exists then there is no guarantee that a * subsequence access will succeed. Care should be taken when using this * method in security sensitive applications. * * @param path * the path to the file to test * @param options * options indicating how symbolic links are handled * . * @return {@code true} if the file exists; {@code false} if the file does * not exist or its existence cannot be determined. * * @throws SecurityException * In the case of the default provider, the {@link * SecurityManager#checkRead(String)} is invoked to check * read access to the file. * * @see #notExists */ public static boolean exists(Path path, LinkOption... options) { try { if (followLinks(options)) { provider(path).checkAccess(path); } else { // attempt to read attributes without following links readAttributes(path, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS); } // file exists return true; } catch (IOException x) { // does not exist or unable to determine if file exists return false; } } /** * Tests whether the file located by this path does not exist. This method * is intended for cases where it is required to take action when it can be * confirmed that a file does not exist. * *

The {@code options} parameter may be used to indicate how symbolic links * are handled for the case that the file is a symbolic link. By default, * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS * NOFOLLOW_LINKS} is present then symbolic links are not followed. * *

Note that this method is not the complement of the {@link #exists * exists} method. Where it is not possible to determine if a file exists * or not then both methods return {@code false}. As with the {@code exists} * method, the result of this method is immediately outdated. If this * method indicates the file does exist then there is no guarantee that a * subsequence attempt to create the file will succeed. Care should be taken * when using this method in security sensitive applications. * * @param path * the path to the file to test * @param options * options indicating how symbolic links are handled * * @return {@code true} if the file does not exist; {@code false} if the * file exists or its existence cannot be determined * * @throws SecurityException * In the case of the default provider, the {@link * SecurityManager#checkRead(String)} is invoked to check * read access to the file. */ public static boolean notExists(Path path, LinkOption... options) { try { if (followLinks(options)) { provider(path).checkAccess(path); } else { // attempt to read attributes without following links readAttributes(path, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS); } // file exists return false; } catch (NoSuchFileException x) { // file confirmed not to exist return true; } catch (IOException x) { return false; } } /** * Used by isReadbale, isWritable, isExecutable to test access to a file. */ private static boolean isAccessible(Path path, AccessMode... modes) { try { provider(path).checkAccess(path, modes); return true; } catch (IOException x) { return false; } } /** * Tests whether a file is readable. This method checks that a file exists * and that this Java virtual machine has appropriate privileges that would * allow it open the file for reading. Depending on the implementation, this * method may require to read file permissions, access control lists, or * other file attributes in order to check the effective access to the file. * Consequently, this method may not be atomic with respect to other file * system operations. * *

Note that the result of this method is immediately outdated, there is * no guarantee that a subsequent attempt to open the file for reading will * succeed (or even that it will access the same file). Care should be taken * when using this method in security sensitive applications. * * @param path * the path to the file to check * * @return {@code true} if the file exists and is readable; {@code false} * if the file does not exist, read access would be denied because * the Java virtual machine has insufficient privileges, or access * cannot be determined * * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * is invoked to check read access to the file. */ public static boolean isReadable(Path path) { return isAccessible(path, AccessMode.READ); } /** * Tests whether a file is writable. This method checks that a file exists * and that this Java virtual machine has appropriate privileges that would * allow it open the file for writing. Depending on the implementation, this * method may require to read file permissions, access control lists, or * other file attributes in order to check the effective access to the file. * Consequently, this method may not be atomic with respect to other file * system operations. * *

Note that result of this method is immediately outdated, there is no * guarantee that a subsequent attempt to open the file for writing will * succeed (or even that it will access the same file). Care should be taken * when using this method in security sensitive applications. * * @param path * the path to the file to check * * @return {@code true} if the file exists and is writable; {@code false} * if the file does not exist, write access would be denied because * the Java virtual machine has insufficient privileges, or access * cannot be determined * * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * is invoked to check write access to the file. */ public static boolean isWritable(Path path) { return isAccessible(path, AccessMode.WRITE); } /** * Tests whether a file is executable. This method checks that a file exists * and that this Java virtual machine has appropriate privileges to {@link * Runtime#exec execute} the file. The semantics may differ when checking * access to a directory. For example, on UNIX systems, checking for * execute access checks that the Java virtual machine has permission to * search the directory in order to access file or subdirectories. * *

Depending on the implementation, this method may require to read file * permissions, access control lists, or other file attributes in order to * check the effective access to the file. Consequently, this method may not * be atomic with respect to other file system operations. * *

Note that the result of this method is immediately outdated, there is * no guarantee that a subsequent attempt to execute the file will succeed * (or even that it will access the same file). Care should be taken when * using this method in security sensitive applications. * * @param path * the path to the file to check * * @return {@code true} if the file exists and is executable; {@code false} * if the file does not exist, execute access would be denied because * the Java virtual machine has insufficient privileges, or access * cannot be determined * * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkExec(String) * checkExec} is invoked to check execute access to the file. */ public static boolean isExecutable(Path path) { return isAccessible(path, AccessMode.EXECUTE); } // -- Recursive operations -- /** * Walks a file tree. * *

This method walks a file tree rooted at a given starting file. The * file tree traversal is depth-first with the given {@link * FileVisitor} invoked for each file encountered. File tree traversal * completes when all accessible files in the tree have been visited, or a * visit method returns a result of {@link FileVisitResult#TERMINATE * TERMINATE}. Where a visit method terminates due an {@code IOException}, * an uncaught error, or runtime exception, then the traversal is terminated * and the error or exception is propagated to the caller of this method. * *

For each file encountered this method attempts to read its {@link * java.nio.file.attribute.BasicFileAttributes}. If the file is not a * directory then the {@link FileVisitor#visitFile visitFile} method is * invoked with the file attributes. If the file attributes cannot be read, * due to an I/O exception, then the {@link FileVisitor#visitFileFailed * visitFileFailed} method is invoked with the I/O exception. * *

Where the file is a directory, and the directory could not be opened, * then the {@code visitFileFailed} method is invoked with the I/O exception, * after which, the file tree walk continues, by default, at the next * sibling of the directory. * *

Where the directory is opened successfully, then the entries in the * directory, and their descendants are visited. When all entries * have been visited, or an I/O error occurs during iteration of the * directory, then the directory is closed and the visitor's {@link * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked. * The file tree walk then continues, by default, at the next sibling * of the directory. * *

By default, symbolic links are not automatically followed by this * method. If the {@code options} parameter contains the {@link * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are * followed. When following links, and the attributes of the target cannot * be read, then this method attempts to get the {@code BasicFileAttributes} * of the link. If they can be read then the {@code visitFile} method is * invoked with the attributes of the link (otherwise the {@code visitFileFailed} * method is invoked as specified above). * *

If the {@code options} parameter contains the {@link * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps * track of directories visited so that cycles can be detected. A cycle * arises when there is an entry in a directory that is an ancestor of the * directory. Cycle detection is done by recording the {@link * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories, * or if file keys are not available, by invoking the {@link #isSameFile * isSameFile} method to test if a directory is the same file as an * ancestor. When a cycle is detected it is treated as an I/O error, and the * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with * an instance of {@link FileSystemLoopException}. * *

The {@code maxDepth} parameter is the maximum number of levels of * directories to visit. A value of {@code 0} means that only the starting * file is visited, unless denied by the security manager. A value of * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all * levels should be visited. The {@code visitFile} method is invoked for all * files, including directories, encountered at {@code maxDepth}, unless the * basic file attributes cannot be read, in which case the {@code * visitFileFailed} method is invoked. * *

If a visitor returns a result of {@code null} then {@code * NullPointerException} is thrown. * *

When a security manager is installed and it denies access to a file * (or directory), then it is ignored and the visitor is not invoked for * that file (or directory). * * @param start * the starting file * @param options * options to configure the traversal * @param maxDepth * the maximum number of directory levels to visit * @param visitor * the file visitor to invoke for each file * * @return the starting file * * @throws IllegalArgumentException * if the {@code maxDepth} parameter is negative * @throws SecurityException * If the security manager denies access to the starting file. * In the case of the default provider, the {@link * SecurityManager#checkRead(String) checkRead} method is invoked * to check read access to the directory. * @throws IOException * if an I/O error is thrown by a visitor method */ public static Path walkFileTree(Path start, Set options, int maxDepth, FileVisitor visitor) throws IOException { if (maxDepth < 0) throw new IllegalArgumentException("'maxDepth' is negative"); new FileTreeWalker(options, visitor, maxDepth).walk(start); return start; } /** * Walks a file tree. * *

This method works as if invoking it were equivalent to evaluating the * expression: *

     * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
     * 
* In other words, it does not follow symbolic links, and visits all levels * of the file tree. * * @param start * the starting file * @param visitor * the file visitor to invoke for each file * * @return the starting file * * @throws SecurityException * If the security manager denies access to the starting file. * In the case of the default provider, the {@link * SecurityManager#checkRead(String) checkRead} method is invoked * to check read access to the directory. * @throws IOException * if an I/O error is thrown by a visitor method */ public static Path walkFileTree(Path start, FileVisitor visitor) throws IOException { return walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor); } // -- Utility methods for simple usages -- // buffer size used for reading and writing private static final int BUFFER_SIZE = 8192; /** * Opens a file for reading, returning a {@code BufferedReader} that may be * used to read text from the file in an efficient manner. Bytes from the * file are decoded into characters using the specified charset. Reading * commences at the beginning of the file. * *

The {@code Reader} methods that read from the file throw {@code * IOException} if a malformed or unmappable byte sequence is read. * * @param path * the path to the file * @param cs * the charset to use for decoding * * @return a new buffered reader, with default buffer size, to read text * from the file * * @throws IOException * if an I/O error occurs opening the file * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. * * @see #readAllLines */ public static BufferedReader newBufferedReader(Path path, Charset cs) throws IOException { CharsetDecoder decoder = cs.newDecoder(); Reader reader = new InputStreamReader(newInputStream(path), decoder); return new BufferedReader(reader); } /** * Opens or creates a file for writing, returning a {@code BufferedWriter} * that may be used to write text to the file in an efficient manner. * The {@code options} parameter specifies how the the file is created or * opened. If no options are present then this method works as if the {@link * StandardOpenOption#CREATE CREATE}, {@link * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link * StandardOpenOption#WRITE WRITE} options are present. In other words, it * opens the file for writing, creating the file if it doesn't exist, or * initially truncating an existing {@link #isRegularFile regular-file} to * a size of {@code 0} if it exists. * *

The {@code Writer} methods to write text throw {@code IOException} * if the text cannot be encoded using the specified charset. * * @param path * the path to the file * @param cs * the charset to use for encoding * @param options * options specifying how the file is opened * * @return a new buffered writer, with default buffer size, to write text * to the file * * @throws IOException * if an I/O error occurs opening or creating the file * @throws UnsupportedOperationException * if an unsupported option is specified * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. * * @see #write(Path,Iterable,Charset,OpenOption[]) */ public static BufferedWriter newBufferedWriter(Path path, Charset cs, OpenOption... options) throws IOException { CharsetEncoder encoder = cs.newEncoder(); Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder); return new BufferedWriter(writer); } /** * Reads all bytes from an input stream and writes them to an output stream. */ private static long copy(InputStream source, OutputStream sink) throws IOException { long nread = 0L; byte[] buf = new byte[BUFFER_SIZE]; int n; while ((n = source.read(buf)) > 0) { sink.write(buf, 0, n); nread += n; } return nread; } /** * Copies all bytes from an input stream to a file. On return, the input * stream will be at end of stream. * *

By default, the copy fails if the target file already exists or is a * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING * REPLACE_EXISTING} option is specified, and the target file already exists, * then it is replaced if it is not a non-empty directory. If the target * file exists and is a symbolic link, then the symbolic link is replaced. * In this release, the {@code REPLACE_EXISTING} option is the only option * required to be supported by this method. Additional options may be * supported in future releases. * *

If an I/O error occurs reading from the input stream or writing to * the file, then it may do so after the target file has been created and * after some bytes have been read or written. Consequently the input * stream may not be at end of stream and may be in an inconsistent state. * It is strongly recommended that the input stream be promptly closed if an * I/O error occurs. * *

This method may block indefinitely reading from the input stream (or * writing to the file). The behavior for the case that the input stream is * asynchronously closed or the thread interrupted during the copy is * highly input stream and file system provider specific and therefore not * specified. * *

Usage example: Suppose we want to capture a web page and save * it to a file: *

     *     Path path = ...
     *     URI u = URI.create("http://java.sun.com/");
     *     try (InputStream in = u.toURL().openStream()) {
     *         Files.copy(in, path);
     *     }
     * 
* * @param in * the input stream to read from * @param target * the path to the file * @param options * options specifying how the copy should be done * * @return the number of bytes read or written * * @throws IOException * if an I/O error occurs when reading or writing * @throws FileAlreadyExistsException * if the target file exists but cannot be replaced because the * {@code REPLACE_EXISTING} option is not specified (optional * specific exception) * @throws DirectoryNotEmptyException * the {@code REPLACE_EXISTING} option is specified but the file * cannot be replaced because it is a non-empty directory * (optional specific exception) * * @throws UnsupportedOperationException * if {@code options} contains a copy option that is not supported * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. Where the * {@code REPLACE_EXISTING} option is specified, the security * manager's {@link SecurityManager#checkDelete(String) checkDelete} * method is invoked to check that an existing file can be deleted. */ public static long copy(InputStream in, Path target, CopyOption... options) throws IOException { // ensure not null before opening file Objects.requireNonNull(in); // check for REPLACE_EXISTING boolean replaceExisting = false; for (CopyOption opt: options) { if (opt == StandardCopyOption.REPLACE_EXISTING) { replaceExisting = true; } else { if (opt == null) { throw new NullPointerException("options contains 'null'"); } else { throw new UnsupportedOperationException(opt + " not supported"); } } } // attempt to delete an existing file SecurityException se = null; if (replaceExisting) { try { deleteIfExists(target); } catch (SecurityException x) { se = x; } } // attempt to create target file. If it fails with // FileAlreadyExistsException then it may be because the security // manager prevented us from deleting the file, in which case we just // throw the SecurityException. OutputStream ostream; try { ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE); } catch (FileAlreadyExistsException x) { if (se != null) throw se; // someone else won the race and created the file throw x; } // do the copy try (OutputStream out = ostream) { return copy(in, out); } } /** * Copies all bytes from a file to an output stream. * *

If an I/O error occurs reading from the file or writing to the output * stream, then it may do so after some bytes have been read or written. * Consequently the output stream may be in an inconsistent state. It is * strongly recommended that the output stream be promptly closed if an I/O * error occurs. * *

This method may block indefinitely writing to the output stream (or * reading from the file). The behavior for the case that the output stream * is asynchronously closed or the thread interrupted during the copy * is highly output stream and file system provider specific and therefore * not specified. * *

Note that if the given output stream is {@link java.io.Flushable} * then its {@link java.io.Flushable#flush flush} method may need to invoked * after this method completes so as to flush any buffered output. * * @param source * the path to the file * @param out * the output stream to write to * * @return the number of bytes read or written * * @throws IOException * if an I/O error occurs when reading or writing * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. */ public static long copy(Path source, OutputStream out) throws IOException { // ensure not null before opening file Objects.requireNonNull(out); try (InputStream in = newInputStream(source)) { return copy(in, out); } } /** * Read all the bytes from an input stream. The {@code initialSize} * parameter indicates the initial size of the byte[] to allocate. */ private static byte[] read(InputStream source, int initialSize) throws IOException { int capacity = initialSize; byte[] buf = new byte[capacity]; int nread = 0; int rem = buf.length; int n; // read to EOF which may read more or less than initialSize (eg: file // is truncated while we are reading) while ((n = source.read(buf, nread, rem)) > 0) { nread += n; rem -= n; assert rem >= 0; if (rem == 0) { // need larger buffer int newCapacity = capacity << 1; if (newCapacity < 0) { if (capacity == Integer.MAX_VALUE) throw new OutOfMemoryError("Required array size too large"); newCapacity = Integer.MAX_VALUE; } rem = newCapacity - capacity; buf = Arrays.copyOf(buf, newCapacity); capacity = newCapacity; } } return (capacity == nread) ? buf : Arrays.copyOf(buf, nread); } /** * Read all the bytes from a file. The method ensures that the file is * closed when all bytes have been read or an I/O error, or other runtime * exception, is thrown. * *

Note that this method is intended for simple cases where it is * convenient to read all bytes into a byte array. It is not intended for * reading in large files. * * @param path * the path to the file * * @return a byte array containing the bytes read from the file * * @throws IOException * if an I/O error occurs reading from the stream * @throws OutOfMemoryError * if an array of the required size cannot be allocated, for * example the file is larger that {@code 2GB} * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. */ public static byte[] readAllBytes(Path path) throws IOException { long size = size(path); if (size > (long)Integer.MAX_VALUE) throw new OutOfMemoryError("Required array size too large"); try (InputStream in = newInputStream(path)) { return read(in, (int)size); } } /** * Read all lines from a file. This method ensures that the file is * closed when all bytes have been read or an I/O error, or other runtime * exception, is thrown. Bytes from the file are decoded into characters * using the specified charset. * *

This method recognizes the following as line terminators: *

    *
  • \u000D followed by \u000A, * CARRIAGE RETURN followed by LINE FEED
  • *
  • \u000A, LINE FEED
  • *
  • \u000D, CARRIAGE RETURN
  • *
*

Additional Unicode line terminators may be recognized in future * releases. * *

Note that this method is intended for simple cases where it is * convenient to read all lines in a single operation. It is not intended * for reading in large files. * * @param path * the path to the file * @param cs * the charset to use for decoding * * @return the lines from the file as a {@code List}; whether the {@code * List} is modifiable or not is implementation dependent and * therefore not specified * * @throws IOException * if an I/O error occurs reading from the file or a malformed or * unmappable byte sequence is read * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. * * @see #newBufferedReader */ public static List readAllLines(Path path, Charset cs) throws IOException { try (BufferedReader reader = newBufferedReader(path, cs)) { List result = new ArrayList<>(); for (;;) { String line = reader.readLine(); if (line == null) break; result.add(line); } return result; } } /** * Writes bytes to a file. The {@code options} parameter specifies how the * the file is created or opened. If no options are present then this method * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link * StandardOpenOption#WRITE WRITE} options are present. In other words, it * opens the file for writing, creating the file if it doesn't exist, or * initially truncating an existing {@link #isRegularFile regular-file} to * a size of {@code 0}. All bytes in the byte array are written to the file. * The method ensures that the file is closed when all bytes have been * written (or an I/O error or other runtime exception is thrown). If an I/O * error occurs then it may do so after the file has created or truncated, * or after some bytes have been written to the file. * *

Usage example: By default the method creates a new file or * overwrites an existing file. Suppose you instead want to append bytes * to an existing file: *

     *     Path path = ...
     *     byte[] bytes = ...
     *     Files.write(path, bytes, StandardOpenOption.APPEND);
     * 
* * @param path * the path to the file * @param bytes * the byte array with the bytes to write * @param options * options specifying how the file is opened * * @return the path * * @throws IOException * if an I/O error occurs writing to or creating the file * @throws UnsupportedOperationException * if an unsupported option is specified * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. */ public static Path write(Path path, byte[] bytes, OpenOption... options) throws IOException { // ensure bytes is not null before opening file Objects.requireNonNull(bytes); try (OutputStream out = Files.newOutputStream(path, options)) { int len = bytes.length; int rem = len; while (rem > 0) { int n = Math.min(rem, BUFFER_SIZE); out.write(bytes, (len-rem), n); rem -= n; } } return path; } /** * Write lines of text to a file. Each line is a char sequence and is * written to the file in sequence with each line terminated by the * platform's line separator, as defined by the system property {@code * line.separator}. Characters are encoded into bytes using the specified * charset. * *

The {@code options} parameter specifies how the the file is created * or opened. If no options are present then this method works as if the * {@link StandardOpenOption#CREATE CREATE}, {@link * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link * StandardOpenOption#WRITE WRITE} options are present. In other words, it * opens the file for writing, creating the file if it doesn't exist, or * initially truncating an existing {@link #isRegularFile regular-file} to * a size of {@code 0}. The method ensures that the file is closed when all * lines have been written (or an I/O error or other runtime exception is * thrown). If an I/O error occurs then it may do so after the file has * created or truncated, or after some bytes have been written to the file. * * @param path * the path to the file * @param lines * an object to iterate over the char sequences * @param cs * the charset to use for encoding * @param options * options specifying how the file is opened * * @return the path * * @throws IOException * if an I/O error occurs writing to or creating the file, or the * text cannot be encoded using the specified charset * @throws UnsupportedOperationException * if an unsupported option is specified * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkWrite(String) checkWrite} * method is invoked to check write access to the file. */ public static Path write(Path path, Iterable lines, Charset cs, OpenOption... options) throws IOException { // ensure lines is not null before opening file Objects.requireNonNull(lines); CharsetEncoder encoder = cs.newEncoder(); OutputStream out = newOutputStream(path, options); try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) { for (CharSequence line: lines) { writer.append(line); writer.newLine(); } } return path; } }