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* 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.
*
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package java.nio.file;
import java.nio.file.attribute.*;
import java.io.IOException;
/**
* Storage for files. A {@code FileStore} represents a storage pool, device,
* partition, volume, concrete file system or other implementation specific means
* of file storage. The {@code FileStore} for where a file is stored is obtained
* by invoking the {@link Files#getFileStore getFileStore} method, or all file
* stores can be enumerated by invoking the {@link FileSystem#getFileStores
* getFileStores} method.
*
* <p> In addition to the methods defined by this class, a file store may support
* one or more {@link FileStoreAttributeView FileStoreAttributeView} classes
* that provide a read-only or updatable view of a set of file store attributes.
*
* @since 1.7
*/
public abstract class FileStore {
/**
* Initializes a new instance of this class.
*/
protected FileStore() {
}
/**
* Returns the name of this file store. The format of the name is highly
* implementation specific. It will typically be the name of the storage
* pool or volume.
*
* <p> The string returned by this method may differ from the string
* returned by the {@link Object#toString() toString} method.
*
* @return the name of this file store
*/
public abstract String name();
/**
* Returns the <em>type</em> of this file store. The format of the string
* returned by this method is highly implementation specific. It may
* indicate, for example, the format used or if the file store is local
* or remote.
*
* @return a string representing the type of this file store
*/
public abstract String type();
/**
* Tells whether this file store is read-only. A file store is read-only if
* it does not support write operations or other changes to files. Any
* attempt to create a file, open an existing file for writing etc. causes
* an {@code IOException} to be thrown.
*
* @return {@code true} if, and only if, this file store is read-only
*/
public abstract boolean isReadOnly();
/**
* Returns the size, in bytes, of the file store.
*
* @return the size of the file store, in bytes
*
* @throws IOException
* if an I/O error occurs
*/
public abstract long getTotalSpace() throws IOException;
/**
* Returns the number of bytes available to this Java virtual machine on the
* file store.
*
* <p> The returned number of available bytes is a hint, but not a
* guarantee, that it is possible to use most or any of these bytes. The
* number of usable bytes is most likely to be accurate immediately
* after the space attributes are obtained. It is likely to be made inaccurate
* by any external I/O operations including those made on the system outside
* of this Java virtual machine.
*
* @return the number of bytes available
*
* @throws IOException
* if an I/O error occurs
*/
public abstract long getUsableSpace() throws IOException;
/**
* Returns the number of unallocated bytes in the file store.
*
* <p> The returned number of unallocated bytes is a hint, but not a
* guarantee, that it is possible to use most or any of these bytes. The
* number of unallocated bytes is most likely to be accurate immediately
* after the space attributes are obtained. It is likely to be
* made inaccurate by any external I/O operations including those made on
* the system outside of this virtual machine.
*
* @return the number of unallocated bytes
*
* @throws IOException
* if an I/O error occurs
*/
public abstract long getUnallocatedSpace() throws IOException;
/**
* Tells whether or not this file store supports the file attributes
* identified by the given file attribute view.
*
* <p> Invoking this method to test if the file store supports {@link
* BasicFileAttributeView} will always return {@code true}. In the case of
* the default provider, this method cannot guarantee to give the correct
* result when the file store is not a local storage device. The reasons for
* this are implementation specific and therefore unspecified.
*
* @param type
* the file attribute view type
*
* @return {@code true} if, and only if, the file attribute view is
* supported
*/
public abstract boolean supportsFileAttributeView(Class<? extends FileAttributeView> type);
/**
* Tells whether or not this file store supports the file attributes
* identified by the given file attribute view.
*
* <p> Invoking this method to test if the file store supports {@link
* BasicFileAttributeView}, identified by the name "{@code basic}" will
* always return {@code true}. In the case of the default provider, this
* method cannot guarantee to give the correct result when the file store is
* not a local storage device. The reasons for this are implementation
* specific and therefore unspecified.
*
* @param name
* the {@link FileAttributeView#name name} of file attribute view
*
* @return {@code true} if, and only if, the file attribute view is
* supported
*/
public abstract boolean supportsFileAttributeView(String name);
/**
* Returns a {@code FileStoreAttributeView} of the given type.
*
* <p> This method is intended to be used where the file store attribute
* view defines type-safe methods to read or update the file store attributes.
* The {@code type} parameter is the type of the attribute view required and
* the method returns an instance of that type if supported.
*
* @param type
* the {@code Class} object corresponding to the attribute view
*
* @return a file store attribute view of the specified type or
* {@code null} if the attribute view is not available
*/
public abstract <V extends FileStoreAttributeView> V
getFileStoreAttributeView(Class<V> type);
/**
* Reads the value of a file store attribute.
*
* <p> The {@code attribute} parameter identifies the attribute to be read
* and takes the form:
* <blockquote>
* <i>view-name</i><b>:</b><i>attribute-name</i>
* </blockquote>
* where the character {@code ':'} stands for itself.
*
* <p> <i>view-name</i> is the {@link FileStoreAttributeView#name name} of
* a {@link FileStore AttributeView} that identifies a set of file attributes.
* <i>attribute-name</i> is the name of the attribute.
*
* <p> <b>Usage Example:</b>
* Suppose we want to know if ZFS compression is enabled (assuming the "zfs"
* view is supported):
* <pre>
* boolean compression = (Boolean)fs.getAttribute("zfs:compression");
* </pre>
*
* @param attribute
* the attribute to read
* @return the attribute value; {@code null} may be a valid valid for some
* attributes
*
* @throws UnsupportedOperationException
* if the attribute view is not available or it does not support
* reading the attribute
* @throws IOException
* if an I/O error occurs
*/
public abstract Object getAttribute(String attribute) throws IOException;
}