arrays.java

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/*
 * @(#)Arrays.java	1.48 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util;

import java.lang.reflect.*;

/**
 * This class contains various methods for manipulating arrays (such as
 * sorting and searching).  This class also contains a static factory 
 * that allows arrays to be viewed as lists.
 *
 * <p>The methods in this class all throw a <tt>NullPointerException</tt> if
 * the specified array reference is null.
 *
 * <p>The documentation for the methods contained in this class includes
 * briefs description of the <i>implementations</i>.  Such descriptions should
 * be regarded as <i>implementation notes</i>, rather than parts of the
 * <i>specification</i>.  Implementors should feel free to substitute other
 * algorithms, so long as the specification itself is adhered to.  (For
 * example, the algorithm used by <tt>sort(Object[])</tt> does not have to be
 * a mergesort, but it does have to be <i>stable</i>.)
 *
 * <p>This class is a member of the 
 * <a href="{@docRoot}/../guide/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author  Josh Bloch
 * @version 1.48, 01/23/03
 * @see     Comparable
 * @see     Comparator
 * @since   1.2
 */

public class Arrays {
    // Suppresses default constructor, ensuring non-instantiability.
    private Arrays() {
    }

    // Sorting

    /**
     * Sorts the specified array of longs into ascending numerical order.
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(long[] a) {
	sort1(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of longs into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)
     *
     * <p>The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     * @param fromIndex the index of the first element (inclusive) to be
     *        sorted.
     * @param toIndex the index of the last element (exclusive) to be sorted.
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     * <tt>toIndex &gt; a.length</tt>
     */
    public static void sort(long[] a, int fromIndex, int toIndex) {
        rangeCheck(a.length, fromIndex, toIndex);
	sort1(a, fromIndex, toIndex-fromIndex);
    }

    /**
     * Sorts the specified array of ints into ascending numerical order.
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(int[] a) {
	sort1(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of ints into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)<p>
     *
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     * @param fromIndex the index of the first element (inclusive) to be
     *        sorted.
     * @param toIndex the index of the last element (exclusive) to be sorted.
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     *	       <tt>toIndex &gt; a.length</tt>
     */
    public static void sort(int[] a, int fromIndex, int toIndex) {
        rangeCheck(a.length, fromIndex, toIndex);
	sort1(a, fromIndex, toIndex-fromIndex);
    }

    /**
     * Sorts the specified array of shorts into ascending numerical order.
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(short[] a) {
	sort1(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of shorts into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)<p>
     *
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     * @param fromIndex the index of the first element (inclusive) to be
     *        sorted.
     * @param toIndex the index of the last element (exclusive) to be sorted.
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     *	       <tt>toIndex &gt; a.length</tt>
     */
    public static void sort(short[] a, int fromIndex, int toIndex) {
        rangeCheck(a.length, fromIndex, toIndex);
	sort1(a, fromIndex, toIndex-fromIndex);
    }

    /**
     * Sorts the specified array of chars into ascending numerical order.
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(char[] a) {
	sort1(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of chars into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)<p>
     *
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     * @param fromIndex the index of the first element (inclusive) to be
     *        sorted.
     * @param toIndex the index of the last element (exclusive) to be sorted.
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     *	       <tt>toIndex &gt; a.length</tt>
     */
    public static void sort(char[] a, int fromIndex, int toIndex) {
        rangeCheck(a.length, fromIndex, toIndex);
	sort1(a, fromIndex, toIndex-fromIndex);
    }

    /**
     * Sorts the specified array of bytes into ascending numerical order.
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(byte[] a) {
	sort1(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of bytes into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)<p>
     *
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     * @param fromIndex the index of the first element (inclusive) to be
     *        sorted.
     * @param toIndex the index of the last element (exclusive) to be sorted.
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     *	       <tt>toIndex &gt; a.length</tt>
     */
    public static void sort(byte[] a, int fromIndex, int toIndex) {
        rangeCheck(a.length, fromIndex, toIndex);
	sort1(a, fromIndex, toIndex-fromIndex);
    }

    /**
     * Sorts the specified array of doubles into ascending numerical order.
     * <p>
     * The <code>&lt;</code> relation does not provide a total order on
     * all floating-point values; although they are distinct numbers
     * <code>-0.0 == 0.0</code> is <code>true</code> and a NaN value
     * compares neither less than, greater than, nor equal to any
     * floating-point value, even itself.  To allow the sort to
     * proceed, instead of using the <code>&lt;</code> relation to
     * determine ascending numerical order, this method uses the total
     * order imposed by {@link Double#compareTo}.  This ordering
     * differs from the <code>&lt;</code> relation in that
     * <code>-0.0</code> is treated as less than <code>0.0</code> and
     * NaN is considered greater than any other floating-point value.
     * For the purposes of sorting, all NaN values are considered
     * equivalent and equal.
     * <p>
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(double[] a) {
	sort2(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of doubles into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)
     * <p>
     * The <code>&lt;</code> relation does not provide a total order on
     * all floating-point values; although they are distinct numbers
     * <code>-0.0 == 0.0</code> is <code>true</code> and a NaN value
     * compares neither less than, greater than, nor equal to any
     * floating-point value, even itself.  To allow the sort to
     * proceed, instead of using the <code>&lt;</code> relation to
     * determine ascending numerical order, this method uses the total
     * order imposed by {@link Double#compareTo}.  This ordering
     * differs from the <code>&lt;</code> relation in that
     * <code>-0.0</code> is treated as less than <code>0.0</code> and
     * NaN is considered greater than any other floating-point value.
     * For the purposes of sorting, all NaN values are considered
     * equivalent and equal.
     * <p>
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     * @param fromIndex the index of the first element (inclusive) to be
     *        sorted.
     * @param toIndex the index of the last element (exclusive) to be sorted.
     * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt>
     * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or
     *	       <tt>toIndex &gt; a.length</tt>
     */
    public static void sort(double[] a, int fromIndex, int toIndex) {
        rangeCheck(a.length, fromIndex, toIndex);
	sort2(a, fromIndex, toIndex);
    }

    /**
     * Sorts the specified array of floats into ascending numerical order.
     * <p>
     * The <code>&lt;</code> relation does not provide a total order on
     * all floating-point values; although they are distinct numbers
     * <code>-0.0f == 0.0f</code> is <code>true</code> and a NaN value
     * compares neither less than, greater than, nor equal to any
     * floating-point value, even itself.  To allow the sort to
     * proceed, instead of using the <code>&lt;</code> relation to
     * determine ascending numerical order, this method uses the total
     * order imposed by {@link Float#compareTo}.  This ordering
     * differs from the <code>&lt;</code> relation in that
     * <code>-0.0f</code> is treated as less than <code>0.0f</code> and
     * NaN is considered greater than any other floating-point value.
     * For the purposes of sorting, all NaN values are considered
     * equivalent and equal.
     * <p>
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.
     */
    public static void sort(float[] a) {
	sort2(a, 0, a.length);
    }

    /**
     * Sorts the specified range of the specified array of floats into
     * ascending numerical order.  The range to be sorted extends from index
     * <tt>fromIndex</tt>, inclusive, to index <tt>toIndex</tt>, exclusive.
     * (If <tt>fromIndex==toIndex</tt>, the range to be sorted is empty.)
     * <p>
     * The <code>&lt;</code> relation does not provide a total order on
     * all floating-point values; although they are distinct numbers
     * <code>-0.0f == 0.0f</code> is <code>true</code> and a NaN value
     * compares neither less than, greater than, nor equal to any
     * floating-point value, even itself.  To allow the sort to
     * proceed, instead of using the <code>&lt;</code> relation to
     * determine ascending numerical order, this method uses the total
     * order imposed by {@link Float#compareTo}.  This ordering
     * differs from the <code>&lt;</code> relation in that
     * <code>-0.0f</code> is treated as less than <code>0.0f</code> and
     * NaN is considered greater than any other floating-point value.
     * For the purposes of sorting, all NaN values are considered
     * equivalent and equal.
     * <p>
     * The sorting algorithm is a tuned quicksort, adapted from Jon
     * L. Bentley and M. Douglas McIlroy's "Engineering a Sort Function",
     * Software-Practice and Experience, Vol. 23(11) P. 1249-1265 (November
     * 1993).  This algorithm offers n*log(n) performance on many data sets
     * that cause other quicksorts to degrade to quadratic performance.
     *
     * @param a the array to be sorted.