Source Code of Java - Long
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/* * %W% %E% * * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */package java.lang;/** * The <code>Long</code> class wraps a value of the primitive type * <code>long</code> in an object. An object of type <code>Long</code> * contains a single field whose type is <code>long</code>. * * <p> * * In addition, this class provides several methods for converting a * <code>long</code> to a <code>String</code> and a * <code>String</code> to a <code>long</code>, as well as other * constants and methods useful when dealing with a <code>long</code>. * * <p>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 <i>Hacker's * Delight</i>, (Addison Wesley, 2002). * * @author Lee Boynton * @author Arthur van Hoff * @author Josh Bloch * @version %I%, %G% * @since JDK1.0 */public final class Long extends Number implements Comparable<Long> { /** * A constant holding the minimum value a <code>long</code> can * have, -2<sup>63</sup>. */ public static final long MIN_VALUE = 0x8000000000000000L; /** * A constant holding the maximum value a <code>long</code> can * have, 2<sup>63</sup>-1. */ public static final long MAX_VALUE = 0x7fffffffffffffffL; /** * The <code>Class</code> instance representing the primitive type * <code>long</code>. * * @since JDK1.1 */ public static final Class<Long> TYPE = (Class<Long>) Class.getPrimitiveClass("long"); /** * Returns a string representation of the first argument in the * radix specified by the second argument. * <p> * If the radix is smaller than <code>Character.MIN_RADIX</code> * or larger than <code>Character.MAX_RADIX</code>, then the radix * <code>10</code> is used instead. * <p> * If the first argument is negative, the first element of the * result is the ASCII minus sign <code>'-'</code> * (<code>'\u002d'</code>). If the first argument is not * negative, no sign character appears in the result. * <p> * 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'</code> * (<code>'\u0030'</code>); otherwise, the first character of * the representation of the magnitude will not be the zero * character. The following ASCII characters are used as digits: * <blockquote><pre> * 0123456789abcdefghijklmnopqrstuvwxyz * </pre></blockquote> * These are <code>'\u0030'</code> through * <code>'\u0039'</code> and <code>'\u0061'</code> through * <code>'\u007a'</code>. If <code>radix</code> is * <var>N</var>, then the first <var>N</var> of these characters * are used as radix-<var>N</var> digits in the order shown. Thus, * the digits for hexadecimal (radix 16) are * <code>0123456789abcdef</code>. If uppercase letters are * desired, the {@link java.lang.String#toUpperCase()} method may * be called on the result: * <blockquote><pre> * Long.toString(n, 16).toUpperCase() * </pre></blockquote> * * @param i a <code>long</code>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</code> * argument as an unsigned integer in base 16. * <p> * The unsigned <code>long</code> value is the argument plus * 2<sup>64</sup> 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</code>s. If the unsigned magnitude is zero, it * is represented by a single zero character <code>'0'</code> * (<code>'\u0030'</code>); 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: * <blockquote><pre> * 0123456789abcdef * </pre></blockquote> * These are the characters <code>'\u0030'</code> through * <code>'\u0039'</code> and <code>'\u0061'</code> through * <code>'\u0066'</code>. If uppercase letters are desired, * the {@link java.lang.String#toUpperCase()} method may be called * on the result: * <blockquote><pre> * Long.toHexString(n).toUpperCase() * </pre></blockquote> * * @param i a <code>long</code> to be converted to a string. * @return the string representation of the unsigned <code>long</code> * 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</code> * argument as an unsigned integer in base 8. * <p> * The unsigned <code>long</code> value is the argument plus * 2<sup>64</sup> 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</code>s. * <p> * If the unsigned magnitude is zero, it is represented by a * single zero character <code>'0'</code> * (<code>'\u0030'</code>); 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: * <blockquote><pre> * 01234567 * </pre></blockquote> * These are the characters <code>'\u0030'</code> through * <code>'\u0037'</code>. * * @param i a <code>long</code> to be converted to a string. * @return the string representation of the unsigned <code>long</code> * 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</code> * argument as an unsigned integer in base 2. * <p> * The unsigned <code>long</code> value is the argument plus * 2<sup>64</sup> 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</code>s. If the unsigned magnitude is zero, it is * represented by a single zero character <code>'0'</code> * (<code>'\u0030'</code>); otherwise, the first character of * the representation of the unsigned magnitude will not be the * zero character. The characters <code>'0'</code> * (<code>'\u0030'</code>) and <code>'1'</code> * (<code>'\u0031'</code>) are used as binary digits. * * @param i a <code>long</code> to be converted to a string. * @return the string representation of the unsigned <code>long</code> * 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</code> object representing the specified * <code>long</code>. 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</code> 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(0, size, buf); } /** * 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; } private static final long MULTMIN_RADIX_TEN = Long.MIN_VALUE / 10; private static final long N_MULTMAX_RADIX_TEN = -Long.MAX_VALUE / 10; /** * Parses the string argument as a signed <code>long</code> 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>'-'</code> (<code>'\u002D'</code>) to * indicate a negative value. The resulting <code>long</code> * value is returned. * <p> * Note that neither the character <code>L</code> * (<code>'\u004C'</code>) nor <code>l</code> * (<code>'\u006C'</code>) 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</code> or <code>l</code> may appear as a digit for a * radix greater than 22. * <p> * An exception of type <code>NumberFormatException</code> is * thrown if any of the following situations occurs: * <ul> * <li>The first argument is <code>null</code> or is a string of * length zero. * <li>The <code>radix</code> is either smaller than {@link * java.lang.Character#MIN_RADIX} or larger than {@link * java.lang.Character#MAX_RADIX}. * <li>Any character of the string is not a digit of the specified * radix, except that the first character may be a minus sign * <code>'-'</code> (<code>'\u002d'</code>) provided that the * string is longer than length 1. * <li>The value represented by the string is not a value of type * <code>long</code>. * </ul><p> * Examples: * <blockquote><pre> * parseLong("0", 10) returns 0L * parseLong("473", 10) returns 473L * 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 * </pre></blockquote> * * @param s the <code>String</code> containing the * <code>long</code> representation to be parsed. * @param radix the radix to be used while parsing <code>s</code>. * @return the <code>long</code> represented by the string argument in * the specified radix. * @exception NumberFormatException if the string does not contain a * parsable <code>long</code>. */ 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, max = s.length(); long limit; long multmin; int digit; if (max > 0) { if (s.charAt(0) == '-') { negative = true; limit = Long.MIN_VALUE; i++; } else { limit = -Long.MAX_VALUE; } if (radix == 10) { multmin = negative ? MULTMIN_RADIX_TEN : N_MULTMAX_RADIX_TEN; } else { multmin = limit / radix; } if (i < max) { digit = Character.digit(s.charAt(i++),radix); if (digit < 0) { throw NumberFormatException.forInputString(s); } else { result = -digit; } } while (i < max) { // 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); } if (negative) { if (i > 1) { return result; } else { /* Only got "-" */ throw NumberFormatException.forInputString(s); } } else { return -result; } } /** * Parses the string argument as a signed decimal * <code>long</code>. The characters in the string must all be * decimal digits, except that the first character may be an ASCII * minus sign <code>'-'</code> (<code>\u002D'</code>) to * indicate a negative value. The resulting <code>long</code> * value is returned, exactly as if the argument and the radix * <code>10</code> were given as arguments to the {@link * #parseLong(java.lang.String, int)} method. * <p> * Note that neither the character <code>L</code> * (<code>'\u004C'</code>) nor <code>l</code> * (<code>'\u006C'</code>) 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</code> containing the <code>long</code> * representation to be parsed * @return the <code>long</code> represented by the argument in * decimal. * @exception NumberFormatException if the string does not contain a * parsable <code>long</code>. */ public static long parseLong(String s) throws NumberFormatException { return parseLong(s, 10); } /** * Returns a <code>Long</code> object holding the value * extracted from the specified <code>String</code> when parsed * with the radix given by the second argument. The first * argument is interpreted as representing a signed * <code>long</code> 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</code> object that represents the <code>long</code> * value specified by the string. * <p> * In other words, this method returns a <code>Long</code> object equal * to the value of: * * <blockquote><code> * new Long(Long.parseLong(s, radix)) * </code></blockquote> * * @param s the string to be parsed * @param radix the radix to be used in interpreting <code>s</code> * @return a <code>Long</code> object holding the value * represented by the string argument in the specified * radix. * @exception NumberFormatException If the <code>String</code> does not * contain a parsable <code>long</code>. */ public static Long valueOf(String s, int radix) throws NumberFormatException { return Long.valueOf(parseLong(s, radix)); } /** * Returns a <code>Long</code> object holding the value * of the specified <code>String</code>. The argument is * interpreted as representing a signed decimal <code>long</code>, * exactly as if the argument were given to the {@link * #parseLong(java.lang.String)} method. The result is a * <code>Long</code> object that represents the integer value * specified by the string. * <p> * In other words, this method returns a <code>Long</code> object * equal to the value of: * * <blockquote><pre> * new Long(Long.parseLong(s)) * </pre></blockquote> * * @param s the string to be parsed. * @return a <code>Long</code> object holding the value * represented by the string argument. * @exception NumberFormatException If the string cannot be parsed * as a <code>long</code>. */ 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 <tt>Long</tt> instance representing the specified * <tt>long</tt> value. * If a new <tt>Long</tt> 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. * * @param l a long value. * @return a <tt>Long</tt> instance representing <tt>l</tt>. * @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</code> into a <code>Long</code>. * Accepts decimal, hexadecimal, and octal numbers given by the * following grammar: * * <blockquote> * <dl> * <dt><i>DecodableString:</i> * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> * <dd><i>Sign<sub>opt</sub></i> <code>0x</code> <i>HexDigits</i> * <dd><i>Sign<sub>opt</sub></i> <code>0X</code> <i>HexDigits</i> * <dd><i>Sign<sub>opt</sub></i> <code>#</code> <i>HexDigits</i> * <dd><i>Sign<sub>opt</sub></i> <code>0</code> <i>OctalDigits</i> * <p> * <dt><i>Sign:</i> * <dd><code>-</code> * </dl> * </blockquote> * * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> * are defined in <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#48282">§3.10.1</a> * of the <a href="http://java.sun.com/docs/books/jls/html/">Java * Language Specification</a>. * <p> * The sequence of characters following an (optional) negative * sign and/or radix specifier ("<code>0x</code>", * "<code>0X</code>", "<code>#</code>", or * leading zero) is parsed as by the <code>Long.parseLong</code> * 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</code> is the * minus sign. No whitespace characters are permitted in the * <code>String</code>. * * @param nm the <code>String</code> to decode. * @return a <code>Long</code> object holding the <code>long</code> * value represented by <code>nm</code> * @exception NumberFormatException if the <code>String</code> does not * contain a parsable <code>long</code>. * @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; // Handle minus sign, if present if (nm.startsWith("-")) { negative = true; 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)) throw new NumberFormatException("Negative sign 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</code>. * * @serial */ private final long value; /** * Constructs a newly allocated <code>Long</code> object that * represents the specified <code>long</code> argument. * * @param value the value to be represented by the * <code>Long</code> object. */ public Long(long value) { this.value = value; } /** * Constructs a newly allocated <code>Long</code> object that * represents the <code>long</code> value indicated by the * <code>String</code> parameter. The string is converted to a * <code>long</code> value in exactly the manner used by the * <code>parseLong</code> method for radix 10. * * @param s the <code>String</code> to be converted to a * <code>Long</code>. * @exception NumberFormatException if the <code>String</code> does not * contain a parsable <code>long</code>. * @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</code> as a * <code>byte</code>. */ public byte byteValue() { return (byte)value; } /** * Returns the value of this <code>Long</code> as a * <code>short</code>. */ public short shortValue() { return (short)value; } /** * Returns the value of this <code>Long</code> as an * <code>int</code>. */ public int intValue() { return (int)value; } /** * Returns the value of this <code>Long</code> as a * <code>long</code> value. */ public long longValue() { return (long)value; } /** * Returns the value of this <code>Long</code> as a * <code>float</code>. */ public float floatValue() { return (float)value; } /** * Returns the value of this <code>Long</code> as a * <code>double</code>. */ public double doubleValue() { return (double)value; } /** * Returns a <code>String</code> object representing this * <code>Long</code>'s value. The value is converted to signed * decimal representation and returned as a string, exactly as if * the <code>long</code> 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 String.valueOf(value); } /** * Returns a hash code for this <code>Long</code>. The result is * the exclusive OR of the two halves of the primitive * <code>long</code> value held by this <code>Long</code> * object. That is, the hashcode is the value of the expression: * <blockquote><pre> * (int)(this.longValue()^(this.longValue()>>>32)) * </pre></blockquote> * * @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</code> if and only if the argument is not * <code>null</code> and is a <code>Long</code> object that * contains the same <code>long</code> value as this object. * * @param obj the object to compare with. * @return <code>true</code> if the objects are the same; * <code>false</code> otherwise. */ public boolean equals(Object obj) { if (obj instanceof Long) { return value == ((Long)obj).longValue(); } return false; } /** * Determines the <code>long</code> value of the system property * with the specified name. * <p> * 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</code> value and a <code>Long</code> object * representing this value is returned. Details of possible * numeric formats can be found with the definition of * <code>getProperty</code>. * <p> * If there is no property with the specified name, if the * specified name is empty or <code>null</code>, or if the * property does not have the correct numeric format, then * <code>null</code> is returned. * <p> * In other words, this method returns a <code>Long</code> object equal to * the value of: * <blockquote><code> * getLong(nm, null) * </code></blockquote> * * @param nm property name. * @return the <code>Long</code> 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</code> value of the system property * with the specified name. * <p> * 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</code> value and a <code>Long</code> object * representing this value is returned. Details of possible * numeric formats can be found with the definition of * <code>getProperty</code>. * <p> * The second argument is the default value. A <code>Long</code> 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. * <p> * In other words, this method returns a <code>Long</code> object equal * to the value of: * <blockquote><code> * getLong(nm, new Long(val)) * </code></blockquote> * but in practice it may be implemented in a manner such as: * <blockquote><pre> * Long result = getLong(nm, null); * return (result == null) ? new Long(val) : result; * </pre></blockquote> * to avoid the unnecessary allocation of a <code>Long</code> object when * the default value is not needed. * * @param nm property name. * @param val default value. * @return the <code>Long</code> 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</code> 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</code> value, as per the * <code>Long.decode</code> method, and a <code>Long</code> object * representing this value is returned. * <p><ul> * <li>If the property value begins with the two ASCII characters * <code>0x</code> or the ASCII character <code>#</code>, not followed by * a minus sign, then the rest of it is parsed as a hexadecimal integer * exactly as for the method {@link #valueOf(java.lang.String, int)} * with radix 16. * <li>If the property value begins with the ASCII character * <code>0</code> followed by another character, it is parsed as * an octal integer exactly as by the method {@link * #valueOf(java.lang.String, int)} with radix 8. * <li>Otherwise the property value is parsed as a decimal * integer exactly as by the method * {@link #valueOf(java.lang.String, int)} with radix 10. * </ul> * <p> * Note that, in every case, neither <code>L</code> * (<code>'\u004C'</code>) nor <code>l</code> * (<code>'\u006C'</code>) 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. * <p> * 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</code>. * * @param nm property name. * @param val default value. * @return the <code>Long</code> 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</code> objects numerically. * * @param anotherLong the <code>Long</code> to be compared. * @return the value <code>0</code> if this <code>Long</code> is * equal to the argument <code>Long</code>; a value less than * <code>0</code> if this <code>Long</code> is numerically less * than the argument <code>Long</code>; and a value greater * than <code>0</code> if this <code>Long</code> is numerically * greater than the argument <code>Long</code> (signed * comparison). * @since 1.2 */ public int compareTo(Long anotherLong) { long thisVal = this.value; long anotherVal = anotherLong.value; return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1)); } // Bit Twiddling /** * The number of bits used to represent a <tt>long</tt> value in two's * complement binary form. * * @since 1.5 */ public static final int SIZE = 64; /** * Returns a <tt>long</tt> value with at most a single one-bit, in the * position of the highest-order ("leftmost") one-bit in the specified * <tt>long</tt> 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 <tt>long</tt> 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 <tt>long</tt> value with at most a single one-bit, in the * position of the lowest-order ("rightmost") one-bit in the specified * <tt>long</tt> 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 <tt>long</tt> 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 <tt>long</tt> 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. * * <p>Note that this method is closely related to the logarithm base 2. * For all positive <tt>long</tt> values x: * <ul> * <li>floor(log<sub>2</sub>(x)) = <tt>63 - numberOfLeadingZeros(x)</tt> * <li>ceil(log<sub>2</sub>(x)) = <tt>64 - numberOfLeadingZeros(x - 1)</tt> * </ul> * * @return the number of zero bits preceding the highest-order * ("leftmost") one-bit in the two's complement binary representation * of the specified <tt>long</tt> 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 * <tt>long</tt> 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 <tt>long</tt> 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 <tt>long</tt> value. This function is * sometimes referred to as the <i>population count</i>. * * @return the number of one-bits in the two's complement binary * representation of the specified <tt>long</tt> 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 <tt>long</tt> 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.) * * <p>Note that left rotation with a negative distance is equivalent to * right rotation: <tt>rotateLeft(val, -distance) == rotateRight(val, * distance)</tt>. 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: <tt>rotateLeft(val, * distance) == rotateLeft(val, distance & 0x3F)</tt>. * * @return the value obtained by rotating the two's complement binary * representation of the specified <tt>long</tt> 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 <tt>long</tt> 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.) * * <p>Note that right rotation with a negative distance is equivalent to * left rotation: <tt>rotateRight(val, -distance) == rotateLeft(val, * distance)</tt>. 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: <tt>rotateRight(val, * distance) == rotateRight(val, distance & 0x3F)</tt>. * * @return the value obtained by rotating the two's complement binary * representation of the specified <tt>long</tt> 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 <tt>long</tt> * value. * * @return the value obtained by reversing order of the bits in the * specified <tt>long</tt> 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 <tt>long</tt> 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 <tt>long</tt> 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 <tt>long</tt> value. * * @return the value obtained by reversing the bytes in the specified * <tt>long</tt> 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;}来源：http://blog.csdn.net/f562867448/article/details/8690916
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