/* * Copyright (c) 1994, 2009, 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.lang; /** * The {@code Long} class wraps a value of the primitive type {@code * long} in an object. An object of type {@code Long} contains a * single field whose type is {@code long}. * *

In addition, this class provides several methods for converting * a {@code long} to a {@code String} and a {@code String} to a {@code * long}, as well as other constants and methods useful when dealing * with a {@code long}. * *

Implementation note: The implementations of the "bit twiddling" * methods (such as {@link #highestOneBit(long) highestOneBit} and * {@link #numberOfTrailingZeros(long) numberOfTrailingZeros}) are * based on material from Henry S. Warren, Jr.'s Hacker's * Delight, (Addison Wesley, 2002). * * @author Lee Boynton * @author Arthur van Hoff * @author Josh Bloch * @author Joseph D. Darcy * @since JDK1.0 */ public final class Long extends Number implements Comparable { /** * A constant holding the minimum value a {@code long} can * have, -263. */ public static final long MIN_VALUE = 0x8000000000000000L; /** * A constant holding the maximum value a {@code long} can * have, 263-1. */ public static final long MAX_VALUE = 0x7fffffffffffffffL; /** * The {@code Class} instance representing the primitive type * {@code long}. * * @since JDK1.1 */ public static final Class TYPE = (Class) Class.getPrimitiveClass("long"); /** * Returns a string representation of the first argument in the * radix specified by the second argument. * *

If the radix is smaller than {@code Character.MIN_RADIX} * or larger than {@code Character.MAX_RADIX}, then the radix * {@code 10} is used instead. * *

If the first argument is negative, the first element of the * result is the ASCII minus sign {@code '-'} * ('\u002d'). If the first argument is not * negative, no sign character appears in the result. * *

The remaining characters of the result represent the magnitude * of the first argument. If the magnitude is zero, it is * represented by a single zero character {@code '0'} * ('\u0030'); otherwise, the first character of * the representation of the magnitude will not be the zero * character. The following ASCII characters are used as digits: * *

* {@code 0123456789abcdefghijklmnopqrstuvwxyz} *
* * These are '\u0030' through * '\u0039' and '\u0061' through * '\u007a'. If {@code radix} is * N, then the first N of these characters * are used as radix-N digits in the order shown. Thus, * the digits for hexadecimal (radix 16) are * {@code 0123456789abcdef}. If uppercase letters are * desired, the {@link java.lang.String#toUpperCase()} method may * be called on the result: * *
* {@code Long.toString(n, 16).toUpperCase()} *
* * @param i a {@code long} to be converted to a string. * @param radix the radix to use in the string representation. * @return a string representation of the argument in the specified radix. * @see java.lang.Character#MAX_RADIX * @see java.lang.Character#MIN_RADIX */ public static String toString(long i, int radix) { if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) radix = 10; if (radix == 10) return toString(i); char[] buf = new char[65]; int charPos = 64; boolean negative = (i < 0); if (!negative) { i = -i; } while (i <= -radix) { buf[charPos--] = Integer.digits[(int)(-(i % radix))]; i = i / radix; } buf[charPos] = Integer.digits[(int)(-i)]; if (negative) { buf[--charPos] = '-'; } return new String(buf, charPos, (65 - charPos)); } /** * Returns a string representation of the {@code long} * argument as an unsigned integer in base 16. * *

The unsigned {@code long} value is the argument plus * 264 if the argument is negative; otherwise, it is * equal to the argument. This value is converted to a string of * ASCII digits in hexadecimal (base 16) with no extra * leading {@code 0}s. If the unsigned magnitude is zero, it * is represented by a single zero character {@code '0'} * ('\u0030'); otherwise, the first character of * the representation of the unsigned magnitude will not be the * zero character. The following characters are used as * hexadecimal digits: * *

* {@code 0123456789abcdef} *
* * These are the characters '\u0030' through * '\u0039' and '\u0061' through * '\u0066'. If uppercase letters are desired, * the {@link java.lang.String#toUpperCase()} method may be called * on the result: * *
* {@code Long.toHexString(n).toUpperCase()} *
* * @param i a {@code long} to be converted to a string. * @return the string representation of the unsigned {@code long} * value represented by the argument in hexadecimal * (base 16). * @since JDK 1.0.2 */ public static String toHexString(long i) { return toUnsignedString(i, 4); } /** * Returns a string representation of the {@code long} * argument as an unsigned integer in base 8. * *

The unsigned {@code long} value is the argument plus * 264 if the argument is negative; otherwise, it is * equal to the argument. This value is converted to a string of * ASCII digits in octal (base 8) with no extra leading * {@code 0}s. * *

If the unsigned magnitude is zero, it is represented by a * single zero character {@code '0'} * ('\u0030'); otherwise, the first character of * the representation of the unsigned magnitude will not be the * zero character. The following characters are used as octal * digits: * *

* {@code 01234567} *
* * These are the characters '\u0030' through * '\u0037'. * * @param i a {@code long} to be converted to a string. * @return the string representation of the unsigned {@code long} * value represented by the argument in octal (base 8). * @since JDK 1.0.2 */ public static String toOctalString(long i) { return toUnsignedString(i, 3); } /** * Returns a string representation of the {@code long} * argument as an unsigned integer in base 2. * *

The unsigned {@code long} value is the argument plus * 264 if the argument is negative; otherwise, it is * equal to the argument. This value is converted to a string of * ASCII digits in binary (base 2) with no extra leading * {@code 0}s. If the unsigned magnitude is zero, it is * represented by a single zero character {@code '0'} * ('\u0030'); otherwise, the first character of * the representation of the unsigned magnitude will not be the * zero character. The characters {@code '0'} * ('\u0030') and {@code '1'} * ('\u0031') are used as binary digits. * * @param i a {@code long} to be converted to a string. * @return the string representation of the unsigned {@code long} * value represented by the argument in binary (base 2). * @since JDK 1.0.2 */ public static String toBinaryString(long i) { return toUnsignedString(i, 1); } /** * Convert the integer to an unsigned number. */ private static String toUnsignedString(long i, int shift) { char[] buf = new char[64]; int charPos = 64; int radix = 1 << shift; long mask = radix - 1; do { buf[--charPos] = Integer.digits[(int)(i & mask)]; i >>>= shift; } while (i != 0); return new String(buf, charPos, (64 - charPos)); } /** * Returns a {@code String} object representing the specified * {@code long}. The argument is converted to signed decimal * representation and returned as a string, exactly as if the * argument and the radix 10 were given as arguments to the {@link * #toString(long, int)} method. * * @param i a {@code long} to be converted. * @return a string representation of the argument in base 10. */ public static String toString(long i) { if (i == Long.MIN_VALUE) return "-9223372036854775808"; int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i); char[] buf = new char[size]; getChars(i, size, buf); return new String(buf, true); } /** * Places characters representing the integer i into the * character array buf. The characters are placed into * the buffer backwards starting with the least significant * digit at the specified index (exclusive), and working * backwards from there. * * Will fail if i == Long.MIN_VALUE */ static void getChars(long i, int index, char[] buf) { long q; int r; int charPos = index; char sign = 0; if (i < 0) { sign = '-'; i = -i; } // Get 2 digits/iteration using longs until quotient fits into an int while (i > Integer.MAX_VALUE) { q = i / 100; // really: r = i - (q * 100); r = (int)(i - ((q << 6) + (q << 5) + (q << 2))); i = q; buf[--charPos] = Integer.DigitOnes[r]; buf[--charPos] = Integer.DigitTens[r]; } // Get 2 digits/iteration using ints int q2; int i2 = (int)i; while (i2 >= 65536) { q2 = i2 / 100; // really: r = i2 - (q * 100); r = i2 - ((q2 << 6) + (q2 << 5) + (q2 << 2)); i2 = q2; buf[--charPos] = Integer.DigitOnes[r]; buf[--charPos] = Integer.DigitTens[r]; } // Fall thru to fast mode for smaller numbers // assert(i2 <= 65536, i2); for (;;) { q2 = (i2 * 52429) >>> (16+3); r = i2 - ((q2 << 3) + (q2 << 1)); // r = i2-(q2*10) ... buf[--charPos] = Integer.digits[r]; i2 = q2; if (i2 == 0) break; } if (sign != 0) { buf[--charPos] = sign; } } // Requires positive x static int stringSize(long x) { long p = 10; for (int i=1; i<19; i++) { if (x < p) return i; p = 10*p; } return 19; } /** * Parses the string argument as a signed {@code long} in the * radix specified by the second argument. The characters in the * string must all be digits of the specified radix (as determined * by whether {@link java.lang.Character#digit(char, int)} returns * a nonnegative value), except that the first character may be an * ASCII minus sign {@code '-'} ('\u002D') to * indicate a negative value or an ASCII plus sign {@code '+'} * ('\u002B') to indicate a positive value. The * resulting {@code long} value is returned. * *

Note that neither the character {@code L} * ('\u004C') nor {@code l} * ('\u006C') is permitted to appear at the end * of the string as a type indicator, as would be permitted in * Java programming language source code - except that either * {@code L} or {@code l} may appear as a digit for a * radix greater than 22. * *

An exception of type {@code NumberFormatException} is * thrown if any of the following situations occurs: *

* *

Examples: *

     * parseLong("0", 10) returns 0L
     * parseLong("473", 10) returns 473L
     * parseLong("+42", 10) returns 42L
     * parseLong("-0", 10) returns 0L
     * parseLong("-FF", 16) returns -255L
     * parseLong("1100110", 2) returns 102L
     * parseLong("99", 8) throws a NumberFormatException
     * parseLong("Hazelnut", 10) throws a NumberFormatException
     * parseLong("Hazelnut", 36) returns 1356099454469L
     * 
* * @param s the {@code String} containing the * {@code long} representation to be parsed. * @param radix the radix to be used while parsing {@code s}. * @return the {@code long} represented by the string argument in * the specified radix. * @throws NumberFormatException if the string does not contain a * parsable {@code long}. */ public static long parseLong(String s, int radix) throws NumberFormatException { if (s == null) { throw new NumberFormatException("null"); } if (radix < Character.MIN_RADIX) { throw new NumberFormatException("radix " + radix + " less than Character.MIN_RADIX"); } if (radix > Character.MAX_RADIX) { throw new NumberFormatException("radix " + radix + " greater than Character.MAX_RADIX"); } long result = 0; boolean negative = false; int i = 0, len = s.length(); long limit = -Long.MAX_VALUE; long multmin; int digit; if (len > 0) { char firstChar = s.charAt(0); if (firstChar < '0') { // Possible leading "+" or "-" if (firstChar == '-') { negative = true; limit = Long.MIN_VALUE; } else if (firstChar != '+') throw NumberFormatException.forInputString(s); if (len == 1) // Cannot have lone "+" or "-" throw NumberFormatException.forInputString(s); i++; } multmin = limit / radix; while (i < len) { // Accumulating negatively avoids surprises near MAX_VALUE digit = Character.digit(s.charAt(i++),radix); if (digit < 0) { throw NumberFormatException.forInputString(s); } if (result < multmin) { throw NumberFormatException.forInputString(s); } result *= radix; if (result < limit + digit) { throw NumberFormatException.forInputString(s); } result -= digit; } } else { throw NumberFormatException.forInputString(s); } return negative ? result : -result; } /** * Parses the string argument as a signed decimal {@code long}. * The characters in the string must all be decimal digits, except * that the first character may be an ASCII minus sign {@code '-'} * (\u002D') to indicate a negative value or an * ASCII plus sign {@code '+'} ('\u002B') to * indicate a positive value. The resulting {@code long} value is * returned, exactly as if the argument and the radix {@code 10} * were given as arguments to the {@link * #parseLong(java.lang.String, int)} method. * *

Note that neither the character {@code L} * ('\u004C') nor {@code l} * ('\u006C') is permitted to appear at the end * of the string as a type indicator, as would be permitted in * Java programming language source code. * * @param s a {@code String} containing the {@code long} * representation to be parsed * @return the {@code long} represented by the argument in * decimal. * @throws NumberFormatException if the string does not contain a * parsable {@code long}. */ public static long parseLong(String s) throws NumberFormatException { return parseLong(s, 10); } /** * Returns a {@code Long} object holding the value * extracted from the specified {@code String} when parsed * with the radix given by the second argument. The first * argument is interpreted as representing a signed * {@code long} in the radix specified by the second * argument, exactly as if the arguments were given to the {@link * #parseLong(java.lang.String, int)} method. The result is a * {@code Long} object that represents the {@code long} * value specified by the string. * *

In other words, this method returns a {@code Long} object equal * to the value of: * *

* {@code new Long(Long.parseLong(s, radix))} *
* * @param s the string to be parsed * @param radix the radix to be used in interpreting {@code s} * @return a {@code Long} object holding the value * represented by the string argument in the specified * radix. * @throws NumberFormatException If the {@code String} does not * contain a parsable {@code long}. */ public static Long valueOf(String s, int radix) throws NumberFormatException { return Long.valueOf(parseLong(s, radix)); } /** * Returns a {@code Long} object holding the value * of the specified {@code String}. The argument is * interpreted as representing a signed decimal {@code long}, * exactly as if the argument were given to the {@link * #parseLong(java.lang.String)} method. The result is a * {@code Long} object that represents the integer value * specified by the string. * *

In other words, this method returns a {@code Long} object * equal to the value of: * *

* {@code new Long(Long.parseLong(s))} *
* * @param s the string to be parsed. * @return a {@code Long} object holding the value * represented by the string argument. * @throws NumberFormatException If the string cannot be parsed * as a {@code long}. */ public static Long valueOf(String s) throws NumberFormatException { return Long.valueOf(parseLong(s, 10)); } private static class LongCache { private LongCache(){} static final Long cache[] = new Long[-(-128) + 127 + 1]; static { for(int i = 0; i < cache.length; i++) cache[i] = new Long(i - 128); } } /** * Returns a {@code Long} instance representing the specified * {@code long} value. * If a new {@code Long} instance is not required, this method * should generally be used in preference to the constructor * {@link #Long(long)}, as this method is likely to yield * significantly better space and time performance by caching * frequently requested values. * * Note that unlike the {@linkplain Integer#valueOf(int) * corresponding method} in the {@code Integer} class, this method * is not required to cache values within a particular * range. * * @param l a long value. * @return a {@code Long} instance representing {@code l}. * @since 1.5 */ public static Long valueOf(long l) { final int offset = 128; if (l >= -128 && l <= 127) { // will cache return LongCache.cache[(int)l + offset]; } return new Long(l); } /** * Decodes a {@code String} into a {@code Long}. * Accepts decimal, hexadecimal, and octal numbers given by the * following grammar: * *
*
*
DecodableString: *
Signopt DecimalNumeral *
Signopt {@code 0x} HexDigits *
Signopt {@code 0X} HexDigits *
Signopt {@code #} HexDigits *
Signopt {@code 0} OctalDigits *

*

Sign: *
{@code -} *
{@code +} *
*
* * DecimalNumeral, HexDigits, and OctalDigits * are as defined in section 3.10.1 of * The Java™ Language Specification, * except that underscores are not accepted between digits. * *

The sequence of characters following an optional * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", * "{@code #}", or leading zero) is parsed as by the {@code * Long.parseLong} method with the indicated radix (10, 16, or 8). * This sequence of characters must represent a positive value or * a {@link NumberFormatException} will be thrown. The result is * negated if first character of the specified {@code String} is * the minus sign. No whitespace characters are permitted in the * {@code String}. * * @param nm the {@code String} to decode. * @return a {@code Long} object holding the {@code long} * value represented by {@code nm} * @throws NumberFormatException if the {@code String} does not * contain a parsable {@code long}. * @see java.lang.Long#parseLong(String, int) * @since 1.2 */ public static Long decode(String nm) throws NumberFormatException { int radix = 10; int index = 0; boolean negative = false; Long result; if (nm.length() == 0) throw new NumberFormatException("Zero length string"); char firstChar = nm.charAt(0); // Handle sign, if present if (firstChar == '-') { negative = true; index++; } else if (firstChar == '+') index++; // Handle radix specifier, if present if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { index += 2; radix = 16; } else if (nm.startsWith("#", index)) { index ++; radix = 16; } else if (nm.startsWith("0", index) && nm.length() > 1 + index) { index ++; radix = 8; } if (nm.startsWith("-", index) || nm.startsWith("+", index)) throw new NumberFormatException("Sign character in wrong position"); try { result = Long.valueOf(nm.substring(index), radix); result = negative ? Long.valueOf(-result.longValue()) : result; } catch (NumberFormatException e) { // If number is Long.MIN_VALUE, we'll end up here. The next line // handles this case, and causes any genuine format error to be // rethrown. String constant = negative ? ("-" + nm.substring(index)) : nm.substring(index); result = Long.valueOf(constant, radix); } return result; } /** * The value of the {@code Long}. * * @serial */ private final long value; /** * Constructs a newly allocated {@code Long} object that * represents the specified {@code long} argument. * * @param value the value to be represented by the * {@code Long} object. */ public Long(long value) { this.value = value; } /** * Constructs a newly allocated {@code Long} object that * represents the {@code long} value indicated by the * {@code String} parameter. The string is converted to a * {@code long} value in exactly the manner used by the * {@code parseLong} method for radix 10. * * @param s the {@code String} to be converted to a * {@code Long}. * @throws NumberFormatException if the {@code String} does not * contain a parsable {@code long}. * @see java.lang.Long#parseLong(java.lang.String, int) */ public Long(String s) throws NumberFormatException { this.value = parseLong(s, 10); } /** * Returns the value of this {@code Long} as a * {@code byte}. */ public byte byteValue() { return (byte)value; } /** * Returns the value of this {@code Long} as a * {@code short}. */ public short shortValue() { return (short)value; } /** * Returns the value of this {@code Long} as an * {@code int}. */ public int intValue() { return (int)value; } /** * Returns the value of this {@code Long} as a * {@code long} value. */ public long longValue() { return (long)value; } /** * Returns the value of this {@code Long} as a * {@code float}. */ public float floatValue() { return (float)value; } /** * Returns the value of this {@code Long} as a * {@code double}. */ public double doubleValue() { return (double)value; } /** * Returns a {@code String} object representing this * {@code Long}'s value. The value is converted to signed * decimal representation and returned as a string, exactly as if * the {@code long} value were given as an argument to the * {@link java.lang.Long#toString(long)} method. * * @return a string representation of the value of this object in * base 10. */ public String toString() { return toString(value); } /** * Returns a hash code for this {@code Long}. The result is * the exclusive OR of the two halves of the primitive * {@code long} value held by this {@code Long} * object. That is, the hashcode is the value of the expression: * *

* {@code (int)(this.longValue()^(this.longValue()>>>32))} *
* * @return a hash code value for this object. */ public int hashCode() { return (int)(value ^ (value >>> 32)); } /** * Compares this object to the specified object. The result is * {@code true} if and only if the argument is not * {@code null} and is a {@code Long} object that * contains the same {@code long} value as this object. * * @param obj the object to compare with. * @return {@code true} if the objects are the same; * {@code false} otherwise. */ public boolean equals(Object obj) { if (obj instanceof Long) { return value == ((Long)obj).longValue(); } return false; } /** * Determines the {@code long} value of the system property * with the specified name. * *

The first argument is treated as the name of a system property. * System properties are accessible through the {@link * java.lang.System#getProperty(java.lang.String)} method. The * string value of this property is then interpreted as a * {@code long} value and a {@code Long} object * representing this value is returned. Details of possible * numeric formats can be found with the definition of * {@code getProperty}. * *

If there is no property with the specified name, if the * specified name is empty or {@code null}, or if the * property does not have the correct numeric format, then * {@code null} is returned. * *

In other words, this method returns a {@code Long} object equal to * the value of: * *

* {@code getLong(nm, null)} *
* * @param nm property name. * @return the {@code Long} value of the property. * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) */ public static Long getLong(String nm) { return getLong(nm, null); } /** * Determines the {@code long} value of the system property * with the specified name. * *

The first argument is treated as the name of a system property. * System properties are accessible through the {@link * java.lang.System#getProperty(java.lang.String)} method. The * string value of this property is then interpreted as a * {@code long} value and a {@code Long} object * representing this value is returned. Details of possible * numeric formats can be found with the definition of * {@code getProperty}. * *

The second argument is the default value. A {@code Long} object * that represents the value of the second argument is returned if there * is no property of the specified name, if the property does not have * the correct numeric format, or if the specified name is empty or null. * *

In other words, this method returns a {@code Long} object equal * to the value of: * *

* {@code getLong(nm, new Long(val))} *
* * but in practice it may be implemented in a manner such as: * *
     * Long result = getLong(nm, null);
     * return (result == null) ? new Long(val) : result;
     * 
* * to avoid the unnecessary allocation of a {@code Long} object when * the default value is not needed. * * @param nm property name. * @param val default value. * @return the {@code Long} value of the property. * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) */ public static Long getLong(String nm, long val) { Long result = Long.getLong(nm, null); return (result == null) ? Long.valueOf(val) : result; } /** * Returns the {@code long} value of the system property with * the specified name. The first argument is treated as the name * of a system property. System properties are accessible through * the {@link java.lang.System#getProperty(java.lang.String)} * method. The string value of this property is then interpreted * as a {@code long} value, as per the * {@code Long.decode} method, and a {@code Long} object * representing this value is returned. * * * *

Note that, in every case, neither {@code L} * ('\u004C') nor {@code l} * ('\u006C') is permitted to appear at the end * of the property value as a type indicator, as would be * permitted in Java programming language source code. * *

The second argument is the default value. The default value is * returned if there is no property of the specified name, if the * property does not have the correct numeric format, or if the * specified name is empty or {@code null}. * * @param nm property name. * @param val default value. * @return the {@code Long} value of the property. * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) * @see java.lang.Long#decode */ public static Long getLong(String nm, Long val) { String v = null; try { v = System.getProperty(nm); } catch (IllegalArgumentException e) { } catch (NullPointerException e) { } if (v != null) { try { return Long.decode(v); } catch (NumberFormatException e) { } } return val; } /** * Compares two {@code Long} objects numerically. * * @param anotherLong the {@code Long} to be compared. * @return the value {@code 0} if this {@code Long} is * equal to the argument {@code Long}; a value less than * {@code 0} if this {@code Long} is numerically less * than the argument {@code Long}; and a value greater * than {@code 0} if this {@code Long} is numerically * greater than the argument {@code Long} (signed * comparison). * @since 1.2 */ public int compareTo(Long anotherLong) { return compare(this.value, anotherLong.value); } /** * Compares two {@code long} values numerically. * The value returned is identical to what would be returned by: *

     *    Long.valueOf(x).compareTo(Long.valueOf(y))
     * 
* * @param x the first {@code long} to compare * @param y the second {@code long} to compare * @return the value {@code 0} if {@code x == y}; * a value less than {@code 0} if {@code x < y}; and * a value greater than {@code 0} if {@code x > y} * @since 1.7 */ public static int compare(long x, long y) { return (x < y) ? -1 : ((x == y) ? 0 : 1); } // Bit Twiddling /** * The number of bits used to represent a {@code long} value in two's * complement binary form. * * @since 1.5 */ public static final int SIZE = 64; /** * Returns a {@code long} value with at most a single one-bit, in the * position of the highest-order ("leftmost") one-bit in the specified * {@code long} value. Returns zero if the specified value has no * one-bits in its two's complement binary representation, that is, if it * is equal to zero. * * @return a {@code long} value with a single one-bit, in the position * of the highest-order one-bit in the specified value, or zero if * the specified value is itself equal to zero. * @since 1.5 */ public static long highestOneBit(long i) { // HD, Figure 3-1 i |= (i >> 1); i |= (i >> 2); i |= (i >> 4); i |= (i >> 8); i |= (i >> 16); i |= (i >> 32); return i - (i >>> 1); } /** * Returns a {@code long} value with at most a single one-bit, in the * position of the lowest-order ("rightmost") one-bit in the specified * {@code long} value. Returns zero if the specified value has no * one-bits in its two's complement binary representation, that is, if it * is equal to zero. * * @return a {@code long} value with a single one-bit, in the position * of the lowest-order one-bit in the specified value, or zero if * the specified value is itself equal to zero. * @since 1.5 */ public static long lowestOneBit(long i) { // HD, Section 2-1 return i & -i; } /** * Returns the number of zero bits preceding the highest-order * ("leftmost") one-bit in the two's complement binary representation * of the specified {@code long} value. Returns 64 if the * specified value has no one-bits in its two's complement representation, * in other words if it is equal to zero. * *

Note that this method is closely related to the logarithm base 2. * For all positive {@code long} values x: *

* * @return the number of zero bits preceding the highest-order * ("leftmost") one-bit in the two's complement binary representation * of the specified {@code long} value, or 64 if the value * is equal to zero. * @since 1.5 */ public static int numberOfLeadingZeros(long i) { // HD, Figure 5-6 if (i == 0) return 64; int n = 1; int x = (int)(i >>> 32); if (x == 0) { n += 32; x = (int)i; } if (x >>> 16 == 0) { n += 16; x <<= 16; } if (x >>> 24 == 0) { n += 8; x <<= 8; } if (x >>> 28 == 0) { n += 4; x <<= 4; } if (x >>> 30 == 0) { n += 2; x <<= 2; } n -= x >>> 31; return n; } /** * Returns the number of zero bits following the lowest-order ("rightmost") * one-bit in the two's complement binary representation of the specified * {@code long} value. Returns 64 if the specified value has no * one-bits in its two's complement representation, in other words if it is * equal to zero. * * @return the number of zero bits following the lowest-order ("rightmost") * one-bit in the two's complement binary representation of the * specified {@code long} value, or 64 if the value is equal * to zero. * @since 1.5 */ public static int numberOfTrailingZeros(long i) { // HD, Figure 5-14 int x, y; if (i == 0) return 64; int n = 63; y = (int)i; if (y != 0) { n = n -32; x = y; } else x = (int)(i>>>32); y = x <<16; if (y != 0) { n = n -16; x = y; } y = x << 8; if (y != 0) { n = n - 8; x = y; } y = x << 4; if (y != 0) { n = n - 4; x = y; } y = x << 2; if (y != 0) { n = n - 2; x = y; } return n - ((x << 1) >>> 31); } /** * Returns the number of one-bits in the two's complement binary * representation of the specified {@code long} value. This function is * sometimes referred to as the population count. * * @return the number of one-bits in the two's complement binary * representation of the specified {@code long} value. * @since 1.5 */ public static int bitCount(long i) { // HD, Figure 5-14 i = i - ((i >>> 1) & 0x5555555555555555L); i = (i & 0x3333333333333333L) + ((i >>> 2) & 0x3333333333333333L); i = (i + (i >>> 4)) & 0x0f0f0f0f0f0f0f0fL; i = i + (i >>> 8); i = i + (i >>> 16); i = i + (i >>> 32); return (int)i & 0x7f; } /** * Returns the value obtained by rotating the two's complement binary * representation of the specified {@code long} value left by the * specified number of bits. (Bits shifted out of the left hand, or * high-order, side reenter on the right, or low-order.) * *

Note that left rotation with a negative distance is equivalent to * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, * distance)}. Note also that rotation by any multiple of 64 is a * no-op, so all but the last six bits of the rotation distance can be * ignored, even if the distance is negative: {@code rotateLeft(val, * distance) == rotateLeft(val, distance & 0x3F)}. * * @return the value obtained by rotating the two's complement binary * representation of the specified {@code long} value left by the * specified number of bits. * @since 1.5 */ public static long rotateLeft(long i, int distance) { return (i << distance) | (i >>> -distance); } /** * Returns the value obtained by rotating the two's complement binary * representation of the specified {@code long} value right by the * specified number of bits. (Bits shifted out of the right hand, or * low-order, side reenter on the left, or high-order.) * *

Note that right rotation with a negative distance is equivalent to * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, * distance)}. Note also that rotation by any multiple of 64 is a * no-op, so all but the last six bits of the rotation distance can be * ignored, even if the distance is negative: {@code rotateRight(val, * distance) == rotateRight(val, distance & 0x3F)}. * * @return the value obtained by rotating the two's complement binary * representation of the specified {@code long} value right by the * specified number of bits. * @since 1.5 */ public static long rotateRight(long i, int distance) { return (i >>> distance) | (i << -distance); } /** * Returns the value obtained by reversing the order of the bits in the * two's complement binary representation of the specified {@code long} * value. * * @return the value obtained by reversing order of the bits in the * specified {@code long} value. * @since 1.5 */ public static long reverse(long i) { // HD, Figure 7-1 i = (i & 0x5555555555555555L) << 1 | (i >>> 1) & 0x5555555555555555L; i = (i & 0x3333333333333333L) << 2 | (i >>> 2) & 0x3333333333333333L; i = (i & 0x0f0f0f0f0f0f0f0fL) << 4 | (i >>> 4) & 0x0f0f0f0f0f0f0f0fL; i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL; i = (i << 48) | ((i & 0xffff0000L) << 16) | ((i >>> 16) & 0xffff0000L) | (i >>> 48); return i; } /** * Returns the signum function of the specified {@code long} value. (The * return value is -1 if the specified value is negative; 0 if the * specified value is zero; and 1 if the specified value is positive.) * * @return the signum function of the specified {@code long} value. * @since 1.5 */ public static int signum(long i) { // HD, Section 2-7 return (int) ((i >> 63) | (-i >>> 63)); } /** * Returns the value obtained by reversing the order of the bytes in the * two's complement representation of the specified {@code long} value. * * @return the value obtained by reversing the bytes in the specified * {@code long} value. * @since 1.5 */ public static long reverseBytes(long i) { i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL; return (i << 48) | ((i & 0xffff0000L) << 16) | ((i >>> 16) & 0xffff0000L) | (i >>> 48); } /** use serialVersionUID from JDK 1.0.2 for interoperability */ private static final long serialVersionUID = 4290774380558885855L; }