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jeremybenn |
/* Integer.java -- object wrapper for int
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Copyright (C) 1998, 1999, 2001, 2002, 2004, 2005
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Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang;
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/**
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* Instances of class <code>Integer</code> represent primitive
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* <code>int</code> values.
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*
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* Additionally, this class provides various helper functions and variables
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* related to ints.
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*
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* @author Paul Fisher
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* @author John Keiser
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* @author Warren Levy
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* @author Eric Blake (ebb9@email.byu.edu)
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* @author Tom Tromey (tromey@redhat.com)
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* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
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* @author Ian Rogers
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* @since 1.0
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* @status updated to 1.5
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*/
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public final class Integer extends Number implements Comparable<Integer>
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{
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/**
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* Compatible with JDK 1.0.2+.
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*/
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private static final long serialVersionUID = 1360826667806852920L;
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/**
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* The minimum value an <code>int</code> can represent is -2147483648 (or
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* -2<sup>31</sup>).
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*/
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public static final int MIN_VALUE = 0x80000000;
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/**
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* The maximum value an <code>int</code> can represent is 2147483647 (or
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* 2<sup>31</sup> - 1).
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*/
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public static final int MAX_VALUE = 0x7fffffff;
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/**
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* The primitive type <code>int</code> is represented by this
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* <code>Class</code> object.
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* @since 1.1
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*/
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public static final Class<Integer> TYPE = (Class<Integer>) VMClassLoader.getPrimitiveClass('I');
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/**
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* The number of bits needed to represent an <code>int</code>.
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* @since 1.5
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*/
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public static final int SIZE = 32;
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// This caches some Integer values, and is used by boxing
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// conversions via valueOf(). We must cache at least -128..127;
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// these constants control how much we actually cache.
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private static final int MIN_CACHE = -128;
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private static final int MAX_CACHE = 127;
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private static final Integer[] intCache = new Integer[MAX_CACHE - MIN_CACHE + 1];
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static
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{
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for (int i=MIN_CACHE; i <= MAX_CACHE; i++)
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intCache[i - MIN_CACHE] = new Integer(i);
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}
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/**
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* The immutable value of this Integer.
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*
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* @serial the wrapped int
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*/
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private final int value;
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/**
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* Create an <code>Integer</code> object representing the value of the
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* <code>int</code> argument.
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*
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* @param value the value to use
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*/
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public Integer(int value)
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{
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this.value = value;
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}
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/**
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* Create an <code>Integer</code> object representing the value of the
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* argument after conversion to an <code>int</code>.
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*
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* @param s the string to convert
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* @throws NumberFormatException if the String does not contain an int
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* @see #valueOf(String)
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*/
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public Integer(String s)
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{
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value = parseInt(s, 10, false);
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}
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/**
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* Return the size of a string large enough to hold the given number
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*
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* @param num the number we want the string length for (must be positive)
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* @param radix the radix (base) that will be used for the string
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* @return a size sufficient for a string of num
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*/
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private static int stringSize(int num, int radix) {
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int exp;
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if (radix < 4)
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{
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exp = 1;
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}
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else if (radix < 8)
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{
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exp = 2;
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}
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else if (radix < 16)
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{
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exp = 3;
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}
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else if (radix < 32)
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{
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exp = 4;
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}
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else
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{
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exp = 5;
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}
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int size=0;
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do
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{
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num >>>= exp;
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size++;
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}
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while(num != 0);
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return size;
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}
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/**
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* Converts the <code>int</code> to a <code>String</code> using
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* the specified radix (base). If the radix exceeds
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* <code>Character.MIN_RADIX</code> or <code>Character.MAX_RADIX</code>, 10
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* is used instead. If the result is negative, the leading character is
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* '-' ('\\u002D'). The remaining characters come from
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* <code>Character.forDigit(digit, radix)</code> ('0'-'9','a'-'z').
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*
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* @param num the <code>int</code> to convert to <code>String</code>
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* @param radix the radix (base) to use in the conversion
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* @return the <code>String</code> representation of the argument
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*/
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public static String toString(int num, int radix)
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{
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if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
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radix = 10;
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// Is the value negative?
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boolean isNeg = num < 0;
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// Is the string a single character?
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if (!isNeg && num < radix)
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return new String(digits, num, 1, true);
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// Compute string size and allocate buffer
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// account for a leading '-' if the value is negative
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int size;
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int i;
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char[] buffer;
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if (isNeg)
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{
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num = -num;
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// When the value is MIN_VALUE, it overflows when made positive
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if (num < 0)
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{
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i = size = stringSize(MAX_VALUE, radix) + 2;
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buffer = new char[size];
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buffer[--i] = digits[(int) (-(num + radix) % radix)];
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num = -(num / radix);
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}
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else
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{
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i = size = stringSize(num, radix) + 1;
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buffer = new char[size];
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}
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}
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else
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{
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i = size = stringSize(num, radix);
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buffer = new char[size];
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}
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do
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{
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buffer[--i] = digits[num % radix];
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num /= radix;
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}
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while (num > 0);
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if (isNeg)
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buffer[--i] = '-';
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// Package constructor avoids an array copy.
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return new String(buffer, i, size - i, true);
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}
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/**
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* Converts the <code>int</code> to a <code>String</code> assuming it is
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* unsigned in base 16.
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*
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* @param i the <code>int</code> to convert to <code>String</code>
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* @return the <code>String</code> representation of the argument
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*/
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public static String toHexString(int i)
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{
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return toUnsignedString(i, 4);
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}
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/**
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* Converts the <code>int</code> to a <code>String</code> assuming it is
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* unsigned in base 8.
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*
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* @param i the <code>int</code> to convert to <code>String</code>
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* @return the <code>String</code> representation of the argument
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*/
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public static String toOctalString(int i)
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{
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return toUnsignedString(i, 3);
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}
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/**
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* Converts the <code>int</code> to a <code>String</code> assuming it is
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* unsigned in base 2.
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*
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* @param i the <code>int</code> to convert to <code>String</code>
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* @return the <code>String</code> representation of the argument
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*/
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public static String toBinaryString(int i)
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{
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return toUnsignedString(i, 1);
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}
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/**
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* Converts the <code>int</code> to a <code>String</code> and assumes
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* a radix of 10.
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*
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* @param i the <code>int</code> to convert to <code>String</code>
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* @return the <code>String</code> representation of the argument
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* @see #toString(int, int)
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*/
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public static String toString(int i)
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{
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// This is tricky: in libgcj, String.valueOf(int) is a fast native
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// implementation. In Classpath it just calls back to
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// Integer.toString(int, int).
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return String.valueOf(i);
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}
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/**
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* Converts the specified <code>String</code> into an <code>int</code>
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* using the specified radix (base). The string must not be <code>null</code>
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* or empty. It may begin with an optional '-', which will negate the answer,
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* provided that there are also valid digits. Each digit is parsed as if by
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* <code>Character.digit(d, radix)</code>, and must be in the range
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* <code>0</code> to <code>radix - 1</code>. Finally, the result must be
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* within <code>MIN_VALUE</code> to <code>MAX_VALUE</code>, inclusive.
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* Unlike Double.parseDouble, you may not have a leading '+'.
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*
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* @param str the <code>String</code> to convert
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* @param radix the radix (base) to use in the conversion
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* @return the <code>String</code> argument converted to <code>int</code>
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* @throws NumberFormatException if <code>s</code> cannot be parsed as an
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* <code>int</code>
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*/
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public static int parseInt(String str, int radix)
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{
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return parseInt(str, radix, false);
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}
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/**
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* Converts the specified <code>String</code> into an <code>int</code>.
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* This function assumes a radix of 10.
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*
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* @param s the <code>String</code> to convert
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* @return the <code>int</code> value of <code>s</code>
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|
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* @throws NumberFormatException if <code>s</code> cannot be parsed as an
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* <code>int</code>
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|
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* @see #parseInt(String, int)
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*/
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public static int parseInt(String s)
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{
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return parseInt(s, 10, false);
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}
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327 |
|
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/**
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329 |
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* Creates a new <code>Integer</code> object using the <code>String</code>
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|
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* and specified radix (base).
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|
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*
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332 |
|
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* @param s the <code>String</code> to convert
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333 |
|
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* @param radix the radix (base) to convert with
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|
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* @return the new <code>Integer</code>
|
335 |
|
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* @throws NumberFormatException if <code>s</code> cannot be parsed as an
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336 |
|
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* <code>int</code>
|
337 |
|
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* @see #parseInt(String, int)
|
338 |
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*/
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public static Integer valueOf(String s, int radix)
|
340 |
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{
|
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return valueOf(parseInt(s, radix, false));
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|
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}
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|
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|
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/**
|
345 |
|
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* Creates a new <code>Integer</code> object using the <code>String</code>,
|
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|
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* assuming a radix of 10.
|
347 |
|
|
*
|
348 |
|
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* @param s the <code>String</code> to convert
|
349 |
|
|
* @return the new <code>Integer</code>
|
350 |
|
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* @throws NumberFormatException if <code>s</code> cannot be parsed as an
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351 |
|
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* <code>int</code>
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352 |
|
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* @see #Integer(String)
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353 |
|
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* @see #parseInt(String)
|
354 |
|
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*/
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355 |
|
|
public static Integer valueOf(String s)
|
356 |
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|
{
|
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|
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return valueOf(parseInt(s, 10, false));
|
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|
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}
|
359 |
|
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|
360 |
|
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/**
|
361 |
|
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* Returns an <code>Integer</code> object wrapping the value.
|
362 |
|
|
* In contrast to the <code>Integer</code> constructor, this method
|
363 |
|
|
* will cache some values. It is used by boxing conversion.
|
364 |
|
|
*
|
365 |
|
|
* @param val the value to wrap
|
366 |
|
|
* @return the <code>Integer</code>
|
367 |
|
|
*/
|
368 |
|
|
public static Integer valueOf(int val)
|
369 |
|
|
{
|
370 |
|
|
if (val < MIN_CACHE || val > MAX_CACHE)
|
371 |
|
|
return new Integer(val);
|
372 |
|
|
else
|
373 |
|
|
return intCache[val - MIN_CACHE];
|
374 |
|
|
}
|
375 |
|
|
|
376 |
|
|
/**
|
377 |
|
|
* Return the value of this <code>Integer</code> as a <code>byte</code>.
|
378 |
|
|
*
|
379 |
|
|
* @return the byte value
|
380 |
|
|
*/
|
381 |
|
|
public byte byteValue()
|
382 |
|
|
{
|
383 |
|
|
return (byte) value;
|
384 |
|
|
}
|
385 |
|
|
|
386 |
|
|
/**
|
387 |
|
|
* Return the value of this <code>Integer</code> as a <code>short</code>.
|
388 |
|
|
*
|
389 |
|
|
* @return the short value
|
390 |
|
|
*/
|
391 |
|
|
public short shortValue()
|
392 |
|
|
{
|
393 |
|
|
return (short) value;
|
394 |
|
|
}
|
395 |
|
|
|
396 |
|
|
/**
|
397 |
|
|
* Return the value of this <code>Integer</code>.
|
398 |
|
|
* @return the int value
|
399 |
|
|
*/
|
400 |
|
|
public int intValue()
|
401 |
|
|
{
|
402 |
|
|
return value;
|
403 |
|
|
}
|
404 |
|
|
|
405 |
|
|
/**
|
406 |
|
|
* Return the value of this <code>Integer</code> as a <code>long</code>.
|
407 |
|
|
*
|
408 |
|
|
* @return the long value
|
409 |
|
|
*/
|
410 |
|
|
public long longValue()
|
411 |
|
|
{
|
412 |
|
|
return value;
|
413 |
|
|
}
|
414 |
|
|
|
415 |
|
|
/**
|
416 |
|
|
* Return the value of this <code>Integer</code> as a <code>float</code>.
|
417 |
|
|
*
|
418 |
|
|
* @return the float value
|
419 |
|
|
*/
|
420 |
|
|
public float floatValue()
|
421 |
|
|
{
|
422 |
|
|
return value;
|
423 |
|
|
}
|
424 |
|
|
|
425 |
|
|
/**
|
426 |
|
|
* Return the value of this <code>Integer</code> as a <code>double</code>.
|
427 |
|
|
*
|
428 |
|
|
* @return the double value
|
429 |
|
|
*/
|
430 |
|
|
public double doubleValue()
|
431 |
|
|
{
|
432 |
|
|
return value;
|
433 |
|
|
}
|
434 |
|
|
|
435 |
|
|
/**
|
436 |
|
|
* Converts the <code>Integer</code> value to a <code>String</code> and
|
437 |
|
|
* assumes a radix of 10.
|
438 |
|
|
*
|
439 |
|
|
* @return the <code>String</code> representation
|
440 |
|
|
*/
|
441 |
|
|
public String toString()
|
442 |
|
|
{
|
443 |
|
|
return String.valueOf(value);
|
444 |
|
|
}
|
445 |
|
|
|
446 |
|
|
/**
|
447 |
|
|
* Return a hashcode representing this Object. <code>Integer</code>'s hash
|
448 |
|
|
* code is simply its value.
|
449 |
|
|
*
|
450 |
|
|
* @return this Object's hash code
|
451 |
|
|
*/
|
452 |
|
|
public int hashCode()
|
453 |
|
|
{
|
454 |
|
|
return value;
|
455 |
|
|
}
|
456 |
|
|
|
457 |
|
|
/**
|
458 |
|
|
* Returns <code>true</code> if <code>obj</code> is an instance of
|
459 |
|
|
* <code>Integer</code> and represents the same int value.
|
460 |
|
|
*
|
461 |
|
|
* @param obj the object to compare
|
462 |
|
|
* @return whether these Objects are semantically equal
|
463 |
|
|
*/
|
464 |
|
|
public boolean equals(Object obj)
|
465 |
|
|
{
|
466 |
|
|
return obj instanceof Integer && value == ((Integer) obj).value;
|
467 |
|
|
}
|
468 |
|
|
|
469 |
|
|
/**
|
470 |
|
|
* Get the specified system property as an <code>Integer</code>. The
|
471 |
|
|
* <code>decode()</code> method will be used to interpret the value of
|
472 |
|
|
* the property.
|
473 |
|
|
*
|
474 |
|
|
* @param nm the name of the system property
|
475 |
|
|
* @return the system property as an <code>Integer</code>, or null if the
|
476 |
|
|
* property is not found or cannot be decoded
|
477 |
|
|
* @throws SecurityException if accessing the system property is forbidden
|
478 |
|
|
* @see System#getProperty(String)
|
479 |
|
|
* @see #decode(String)
|
480 |
|
|
*/
|
481 |
|
|
public static Integer getInteger(String nm)
|
482 |
|
|
{
|
483 |
|
|
return getInteger(nm, null);
|
484 |
|
|
}
|
485 |
|
|
|
486 |
|
|
/**
|
487 |
|
|
* Get the specified system property as an <code>Integer</code>, or use a
|
488 |
|
|
* default <code>int</code> value if the property is not found or is not
|
489 |
|
|
* decodable. The <code>decode()</code> method will be used to interpret
|
490 |
|
|
* the value of the property.
|
491 |
|
|
*
|
492 |
|
|
* @param nm the name of the system property
|
493 |
|
|
* @param val the default value
|
494 |
|
|
* @return the value of the system property, or the default
|
495 |
|
|
* @throws SecurityException if accessing the system property is forbidden
|
496 |
|
|
* @see System#getProperty(String)
|
497 |
|
|
* @see #decode(String)
|
498 |
|
|
*/
|
499 |
|
|
public static Integer getInteger(String nm, int val)
|
500 |
|
|
{
|
501 |
|
|
Integer result = getInteger(nm, null);
|
502 |
|
|
return result == null ? valueOf(val) : result;
|
503 |
|
|
}
|
504 |
|
|
|
505 |
|
|
/**
|
506 |
|
|
* Get the specified system property as an <code>Integer</code>, or use a
|
507 |
|
|
* default <code>Integer</code> value if the property is not found or is
|
508 |
|
|
* not decodable. The <code>decode()</code> method will be used to
|
509 |
|
|
* interpret the value of the property.
|
510 |
|
|
*
|
511 |
|
|
* @param nm the name of the system property
|
512 |
|
|
* @param def the default value
|
513 |
|
|
* @return the value of the system property, or the default
|
514 |
|
|
* @throws SecurityException if accessing the system property is forbidden
|
515 |
|
|
* @see System#getProperty(String)
|
516 |
|
|
* @see #decode(String)
|
517 |
|
|
*/
|
518 |
|
|
public static Integer getInteger(String nm, Integer def)
|
519 |
|
|
{
|
520 |
|
|
if (nm == null || "".equals(nm))
|
521 |
|
|
return def;
|
522 |
|
|
nm = System.getProperty(nm);
|
523 |
|
|
if (nm == null)
|
524 |
|
|
return def;
|
525 |
|
|
try
|
526 |
|
|
{
|
527 |
|
|
return decode(nm);
|
528 |
|
|
}
|
529 |
|
|
catch (NumberFormatException e)
|
530 |
|
|
{
|
531 |
|
|
return def;
|
532 |
|
|
}
|
533 |
|
|
}
|
534 |
|
|
|
535 |
|
|
/**
|
536 |
|
|
* Convert the specified <code>String</code> into an <code>Integer</code>.
|
537 |
|
|
* The <code>String</code> may represent decimal, hexadecimal, or
|
538 |
|
|
* octal numbers.
|
539 |
|
|
*
|
540 |
|
|
* <p>The extended BNF grammar is as follows:<br>
|
541 |
|
|
* <pre>
|
542 |
|
|
* <em>DecodableString</em>:
|
543 |
|
|
* ( [ <code>-</code> ] <em>DecimalNumber</em> )
|
544 |
|
|
* | ( [ <code>-</code> ] ( <code>0x</code> | <code>0X</code>
|
545 |
|
|
* | <code>#</code> ) <em>HexDigit</em> { <em>HexDigit</em> } )
|
546 |
|
|
* | ( [ <code>-</code> ] <code>0</code> { <em>OctalDigit</em> } )
|
547 |
|
|
* <em>DecimalNumber</em>:
|
548 |
|
|
* <em>DecimalDigit except '0'</em> { <em>DecimalDigit</em> }
|
549 |
|
|
* <em>DecimalDigit</em>:
|
550 |
|
|
* <em>Character.digit(d, 10) has value 0 to 9</em>
|
551 |
|
|
* <em>OctalDigit</em>:
|
552 |
|
|
* <em>Character.digit(d, 8) has value 0 to 7</em>
|
553 |
|
|
* <em>DecimalDigit</em>:
|
554 |
|
|
* <em>Character.digit(d, 16) has value 0 to 15</em>
|
555 |
|
|
* </pre>
|
556 |
|
|
* Finally, the value must be in the range <code>MIN_VALUE</code> to
|
557 |
|
|
* <code>MAX_VALUE</code>, or an exception is thrown.
|
558 |
|
|
*
|
559 |
|
|
* @param str the <code>String</code> to interpret
|
560 |
|
|
* @return the value of the String as an <code>Integer</code>
|
561 |
|
|
* @throws NumberFormatException if <code>s</code> cannot be parsed as a
|
562 |
|
|
* <code>int</code>
|
563 |
|
|
* @throws NullPointerException if <code>s</code> is null
|
564 |
|
|
* @since 1.2
|
565 |
|
|
*/
|
566 |
|
|
public static Integer decode(String str)
|
567 |
|
|
{
|
568 |
|
|
return valueOf(parseInt(str, 10, true));
|
569 |
|
|
}
|
570 |
|
|
|
571 |
|
|
/**
|
572 |
|
|
* Compare two Integers numerically by comparing their <code>int</code>
|
573 |
|
|
* values. The result is positive if the first is greater, negative if the
|
574 |
|
|
* second is greater, and 0 if the two are equal.
|
575 |
|
|
*
|
576 |
|
|
* @param i the Integer to compare
|
577 |
|
|
* @return the comparison
|
578 |
|
|
* @since 1.2
|
579 |
|
|
*/
|
580 |
|
|
public int compareTo(Integer i)
|
581 |
|
|
{
|
582 |
|
|
if (value == i.value)
|
583 |
|
|
return 0;
|
584 |
|
|
// Returns just -1 or 1 on inequality; doing math might overflow.
|
585 |
|
|
return value > i.value ? 1 : -1;
|
586 |
|
|
}
|
587 |
|
|
|
588 |
|
|
/**
|
589 |
|
|
* Return the number of bits set in x.
|
590 |
|
|
* @param x value to examine
|
591 |
|
|
* @since 1.5
|
592 |
|
|
*/
|
593 |
|
|
public static int bitCount(int x)
|
594 |
|
|
{
|
595 |
|
|
// Successively collapse alternating bit groups into a sum.
|
596 |
|
|
x = ((x >> 1) & 0x55555555) + (x & 0x55555555);
|
597 |
|
|
x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
|
598 |
|
|
x = ((x >> 4) & 0x0f0f0f0f) + (x & 0x0f0f0f0f);
|
599 |
|
|
x = ((x >> 8) & 0x00ff00ff) + (x & 0x00ff00ff);
|
600 |
|
|
return ((x >> 16) & 0x0000ffff) + (x & 0x0000ffff);
|
601 |
|
|
}
|
602 |
|
|
|
603 |
|
|
/**
|
604 |
|
|
* Rotate x to the left by distance bits.
|
605 |
|
|
* @param x the value to rotate
|
606 |
|
|
* @param distance the number of bits by which to rotate
|
607 |
|
|
* @since 1.5
|
608 |
|
|
*/
|
609 |
|
|
public static int rotateLeft(int x, int distance)
|
610 |
|
|
{
|
611 |
|
|
// This trick works because the shift operators implicitly mask
|
612 |
|
|
// the shift count.
|
613 |
|
|
return (x << distance) | (x >>> - distance);
|
614 |
|
|
}
|
615 |
|
|
|
616 |
|
|
/**
|
617 |
|
|
* Rotate x to the right by distance bits.
|
618 |
|
|
* @param x the value to rotate
|
619 |
|
|
* @param distance the number of bits by which to rotate
|
620 |
|
|
* @since 1.5
|
621 |
|
|
*/
|
622 |
|
|
public static int rotateRight(int x, int distance)
|
623 |
|
|
{
|
624 |
|
|
// This trick works because the shift operators implicitly mask
|
625 |
|
|
// the shift count.
|
626 |
|
|
return (x << - distance) | (x >>> distance);
|
627 |
|
|
}
|
628 |
|
|
|
629 |
|
|
/**
|
630 |
|
|
* Find the highest set bit in value, and return a new value
|
631 |
|
|
* with only that bit set.
|
632 |
|
|
* @param value the value to examine
|
633 |
|
|
* @since 1.5
|
634 |
|
|
*/
|
635 |
|
|
public static int highestOneBit(int value)
|
636 |
|
|
{
|
637 |
|
|
value |= value >>> 1;
|
638 |
|
|
value |= value >>> 2;
|
639 |
|
|
value |= value >>> 4;
|
640 |
|
|
value |= value >>> 8;
|
641 |
|
|
value |= value >>> 16;
|
642 |
|
|
return value ^ (value >>> 1);
|
643 |
|
|
}
|
644 |
|
|
|
645 |
|
|
/**
|
646 |
|
|
* Return the number of leading zeros in value.
|
647 |
|
|
* @param value the value to examine
|
648 |
|
|
* @since 1.5
|
649 |
|
|
*/
|
650 |
|
|
public static int numberOfLeadingZeros(int value)
|
651 |
|
|
{
|
652 |
|
|
value |= value >>> 1;
|
653 |
|
|
value |= value >>> 2;
|
654 |
|
|
value |= value >>> 4;
|
655 |
|
|
value |= value >>> 8;
|
656 |
|
|
value |= value >>> 16;
|
657 |
|
|
return bitCount(~value);
|
658 |
|
|
}
|
659 |
|
|
|
660 |
|
|
/**
|
661 |
|
|
* Find the lowest set bit in value, and return a new value
|
662 |
|
|
* with only that bit set.
|
663 |
|
|
* @param value the value to examine
|
664 |
|
|
* @since 1.5
|
665 |
|
|
*/
|
666 |
|
|
public static int lowestOneBit(int value)
|
667 |
|
|
{
|
668 |
|
|
// Classic assembly trick.
|
669 |
|
|
return value & - value;
|
670 |
|
|
}
|
671 |
|
|
|
672 |
|
|
/**
|
673 |
|
|
* Find the number of trailing zeros in value.
|
674 |
|
|
* @param value the value to examine
|
675 |
|
|
* @since 1.5
|
676 |
|
|
*/
|
677 |
|
|
public static int numberOfTrailingZeros(int value)
|
678 |
|
|
{
|
679 |
|
|
return bitCount((value & -value) - 1);
|
680 |
|
|
}
|
681 |
|
|
|
682 |
|
|
/**
|
683 |
|
|
* Return 1 if x is positive, -1 if it is negative, and 0 if it is
|
684 |
|
|
* zero.
|
685 |
|
|
* @param x the value to examine
|
686 |
|
|
* @since 1.5
|
687 |
|
|
*/
|
688 |
|
|
public static int signum(int x)
|
689 |
|
|
{
|
690 |
|
|
return (x >> 31) | (-x >>> 31);
|
691 |
|
|
|
692 |
|
|
// The LHS propagates the sign bit through every bit in the word;
|
693 |
|
|
// if X < 0, every bit is set to 1, else 0. if X > 0, the RHS
|
694 |
|
|
// negates x and shifts the resulting 1 in the sign bit to the
|
695 |
|
|
// LSB, leaving every other bit 0.
|
696 |
|
|
|
697 |
|
|
// Hacker's Delight, Section 2-7
|
698 |
|
|
}
|
699 |
|
|
|
700 |
|
|
/**
|
701 |
|
|
* Reverse the bytes in val.
|
702 |
|
|
* @since 1.5
|
703 |
|
|
*/
|
704 |
|
|
public static int reverseBytes(int val)
|
705 |
|
|
{
|
706 |
|
|
return ( ((val >> 24) & 0xff)
|
707 |
|
|
| ((val >> 8) & 0xff00)
|
708 |
|
|
| ((val << 8) & 0xff0000)
|
709 |
|
|
| ((val << 24) & 0xff000000));
|
710 |
|
|
}
|
711 |
|
|
|
712 |
|
|
/**
|
713 |
|
|
* Reverse the bits in val.
|
714 |
|
|
* @since 1.5
|
715 |
|
|
*/
|
716 |
|
|
public static int reverse(int val)
|
717 |
|
|
{
|
718 |
|
|
// Successively swap alternating bit groups.
|
719 |
|
|
val = ((val >> 1) & 0x55555555) + ((val << 1) & ~0x55555555);
|
720 |
|
|
val = ((val >> 2) & 0x33333333) + ((val << 2) & ~0x33333333);
|
721 |
|
|
val = ((val >> 4) & 0x0f0f0f0f) + ((val << 4) & ~0x0f0f0f0f);
|
722 |
|
|
val = ((val >> 8) & 0x00ff00ff) + ((val << 8) & ~0x00ff00ff);
|
723 |
|
|
return ((val >> 16) & 0x0000ffff) + ((val << 16) & ~0x0000ffff);
|
724 |
|
|
}
|
725 |
|
|
|
726 |
|
|
/**
|
727 |
|
|
* Helper for converting unsigned numbers to String.
|
728 |
|
|
*
|
729 |
|
|
* @param num the number
|
730 |
|
|
* @param exp log2(digit) (ie. 1, 3, or 4 for binary, oct, hex)
|
731 |
|
|
*/
|
732 |
|
|
// Package visible for use by Long.
|
733 |
|
|
static String toUnsignedString(int num, int exp)
|
734 |
|
|
{
|
735 |
|
|
// Compute string length
|
736 |
|
|
int size = 1;
|
737 |
|
|
int copy = num >>> exp;
|
738 |
|
|
while (copy != 0)
|
739 |
|
|
{
|
740 |
|
|
size++;
|
741 |
|
|
copy >>>= exp;
|
742 |
|
|
}
|
743 |
|
|
// Quick path for single character strings
|
744 |
|
|
if (size == 1)
|
745 |
|
|
return new String(digits, num, 1, true);
|
746 |
|
|
|
747 |
|
|
// Encode into buffer
|
748 |
|
|
int mask = (1 << exp) - 1;
|
749 |
|
|
char[] buffer = new char[size];
|
750 |
|
|
int i = size;
|
751 |
|
|
do
|
752 |
|
|
{
|
753 |
|
|
buffer[--i] = digits[num & mask];
|
754 |
|
|
num >>>= exp;
|
755 |
|
|
}
|
756 |
|
|
while (num != 0);
|
757 |
|
|
|
758 |
|
|
// Package constructor avoids an array copy.
|
759 |
|
|
return new String(buffer, i, size - i, true);
|
760 |
|
|
}
|
761 |
|
|
|
762 |
|
|
/**
|
763 |
|
|
* Helper for parsing ints, used by Integer, Short, and Byte.
|
764 |
|
|
*
|
765 |
|
|
* @param str the string to parse
|
766 |
|
|
* @param radix the radix to use, must be 10 if decode is true
|
767 |
|
|
* @param decode if called from decode
|
768 |
|
|
* @return the parsed int value
|
769 |
|
|
* @throws NumberFormatException if there is an error
|
770 |
|
|
* @throws NullPointerException if decode is true and str if null
|
771 |
|
|
* @see #parseInt(String, int)
|
772 |
|
|
* @see #decode(String)
|
773 |
|
|
* @see Byte#parseByte(String, int)
|
774 |
|
|
* @see Short#parseShort(String, int)
|
775 |
|
|
*/
|
776 |
|
|
static int parseInt(String str, int radix, boolean decode)
|
777 |
|
|
{
|
778 |
|
|
if (! decode && str == null)
|
779 |
|
|
throw new NumberFormatException();
|
780 |
|
|
int index = 0;
|
781 |
|
|
int len = str.length();
|
782 |
|
|
boolean isNeg = false;
|
783 |
|
|
if (len == 0)
|
784 |
|
|
throw new NumberFormatException("string length is null");
|
785 |
|
|
int ch = str.charAt(index);
|
786 |
|
|
if (ch == '-')
|
787 |
|
|
{
|
788 |
|
|
if (len == 1)
|
789 |
|
|
throw new NumberFormatException("pure '-'");
|
790 |
|
|
isNeg = true;
|
791 |
|
|
ch = str.charAt(++index);
|
792 |
|
|
}
|
793 |
|
|
else if (ch == '+')
|
794 |
|
|
{
|
795 |
|
|
if (len == 1)
|
796 |
|
|
throw new NumberFormatException("pure '+'");
|
797 |
|
|
ch = str.charAt(++index);
|
798 |
|
|
}
|
799 |
|
|
if (decode)
|
800 |
|
|
{
|
801 |
|
|
if (ch == '0')
|
802 |
|
|
{
|
803 |
|
|
if (++index == len)
|
804 |
|
|
return 0;
|
805 |
|
|
if ((str.charAt(index) & ~('x' ^ 'X')) == 'X')
|
806 |
|
|
{
|
807 |
|
|
radix = 16;
|
808 |
|
|
index++;
|
809 |
|
|
}
|
810 |
|
|
else
|
811 |
|
|
radix = 8;
|
812 |
|
|
}
|
813 |
|
|
else if (ch == '#')
|
814 |
|
|
{
|
815 |
|
|
radix = 16;
|
816 |
|
|
index++;
|
817 |
|
|
}
|
818 |
|
|
}
|
819 |
|
|
if (index == len)
|
820 |
|
|
throw new NumberFormatException("non terminated number: " + str);
|
821 |
|
|
|
822 |
|
|
int max = MAX_VALUE / radix;
|
823 |
|
|
// We can't directly write `max = (MAX_VALUE + 1) / radix'.
|
824 |
|
|
// So instead we fake it.
|
825 |
|
|
if (isNeg && MAX_VALUE % radix == radix - 1)
|
826 |
|
|
++max;
|
827 |
|
|
|
828 |
|
|
int val = 0;
|
829 |
|
|
while (index < len)
|
830 |
|
|
{
|
831 |
|
|
if (val < 0 || val > max)
|
832 |
|
|
throw new NumberFormatException("number overflow (pos=" + index + ") : " + str);
|
833 |
|
|
|
834 |
|
|
ch = Character.digit(str.charAt(index++), radix);
|
835 |
|
|
val = val * radix + ch;
|
836 |
|
|
if (ch < 0 || (val < 0 && (! isNeg || val != MIN_VALUE)))
|
837 |
|
|
throw new NumberFormatException("invalid character at position " + index + " in " + str);
|
838 |
|
|
}
|
839 |
|
|
return isNeg ? -val : val;
|
840 |
|
|
}
|
841 |
|
|
}
|