arrayutils.java

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/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
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 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
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 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
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package org.apache.commons.lang;

import java.util.HashMap;
import java.util.Map;

import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.commons.lang.builder.ToStringStyle;

/**
 * <p>Operations on arrays, primitive arrays (like <code>int[]</code>) and primitive wrapper arrays 
 * (like <code>Integer[]</code>).</p>
 * 
 * <p>This class tries to handle <code>null</code> input gracefully.
 * An exception will not be thrown for a <code>null</code>
 * array input. However, an Object array that contains a <code>null</code>
 * element may throw an exception. Each method documents its behaviour.</p>
 *
 * @author Stephen Colebourne
 * @author Moritz Petersen
 * @author <a href="mailto:[e-mail]">Fredrik Westermarck</a>
 * @author Nikolay Metchev
 * @author Matthew Hawthorne
 * @author Tim O'Brien
 * @author Pete Gieser
 * @author Gary Gregory
 * @since 2.0
 * @version $Id: ArrayUtils.java,v 1.25 2003/08/22 17:25:33 ggregory Exp $
 */
public class ArrayUtils {

    /**
     * An empty immutable <code>Object</code> array.
     */
    public static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];
    /**
     * An empty immutable <code>Class</code> array.
     */
    public static final Class[] EMPTY_CLASS_ARRAY = new Class[0];
    /**
     * An empty immutable <code>String</code> array.
     */
    public static final String[] EMPTY_STRING_ARRAY = new String[0];
    /**
     * An empty immutable <code>long</code> array.
     */
    public static final long[] EMPTY_LONG_ARRAY = new long[0];
    /**
     * An empty immutable <code>Long</code> array.
     */
    public static final Long[] EMPTY_LONG_OBJECT_ARRAY = new Long[0];
    /**
     * An empty immutable <code>int</code> array.
     */
    public static final int[] EMPTY_INT_ARRAY = new int[0];
    /**
     * An empty immutable <code>Integer</code> array.
     */
    public static final Integer[] EMPTY_INTEGER_OBJECT_ARRAY = new Integer[0];
    /**
     * An empty immutable <code>short</code> array.
     */
    public static final short[] EMPTY_SHORT_ARRAY = new short[0];
    /**
     * An empty immutable <code>Short</code> array.
     */
    public static final Short[] EMPTY_SHORT_OBJECT_ARRAY = new Short[0];
    /**
     * An empty immutable <code>byte</code> array.
     */
    public static final byte[] EMPTY_BYTE_ARRAY = new byte[0];
    /**
     * An empty immutable <code>Byte</code> array.
     */
    public static final Byte[] EMPTY_BYTE_OBJECT_ARRAY = new Byte[0];
    /**
     * An empty immutable <code>double</code> array.
     */
    public static final double[] EMPTY_DOUBLE_ARRAY = new double[0];
    /**
     * An empty immutable <code>Double</code> array.
     */
    public static final Double[] EMPTY_DOUBLE_OBJECT_ARRAY = new Double[0];
    /**
     * An empty immutable <code>float</code> array.
     */
    public static final float[] EMPTY_FLOAT_ARRAY = new float[0];
    /**
     * An empty immutable <code>Float</code> array.
     */
    public static final Float[] EMPTY_FLOAT_OBJECT_ARRAY = new Float[0];
    /**
     * An empty immutable <code>boolean</code> array.
     */
    public static final boolean[] EMPTY_BOOLEAN_ARRAY = new boolean[0];
    /**
     * An empty immutable <code>Boolean</code> array.
     */
    public static final Boolean[] EMPTY_BOOLEAN_OBJECT_ARRAY = new Boolean[0];
    /**
     * An empty immutable <code>char</code> array.
     */
    public static final char[] EMPTY_CHAR_ARRAY = new char[0];
    /**
     * An empty immutable <code>Character</code> array.
     */
    public static final Character[] EMPTY_CHARACTER_OBJECT_ARRAY = new Character[0];

    /**
     * <p>ArrayUtils instances should NOT be constructed in standard programming.
     * Instead, the class should be used as <code>ArrayUtils.clone(new int[] {2})</code>.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean instance
     * to operate.</p>
     */
    public ArrayUtils() {
    }
    
    // Basic methods handling multi-dimensional arrays
    //-----------------------------------------------------------------------
    /**
     * <p>Outputs an array as a String, treating <code>null</code> as an empty array.</p>
     *
     * <p>Multi-dimensional arrays are handled correctly, including
     * multi-dimensional primitive arrays.</p>
     *
     * <p>The format is that of Java source code, for example <code>{a,b}</code>.</p>
     * 
     * @param array  the array to get a toString for, may be <code>null</code>
     * @return a String representation of the array, '{}' if null array input
     */
    public static String toString(final Object array) {
        return toString(array, "{}");
    }

    /**
     * <p>Outputs an array as a String handling <code>null</code>s.</p>
     *
     * <p>Multi-dimensional arrays are handled correctly, including
     * multi-dimensional primitive arrays.</p>
     *
     * <p>The format is that of Java source code, for example <code>{a,b}</code>.</p>
     * 
     * @param array  the array to get a toString for, may be <code>null</code>
     * @param stringIfNull  the String to return if the array is <code>null</code>
     * @return a String representation of the array
     */    
    public static String toString(final Object array, final String stringIfNull) {
        if (array == null) {
            return stringIfNull;
        }
        return new ToStringBuilder(array, ToStringStyle.SIMPLE_STYLE).append(array).toString();
    }

    /**
     * <p>Get a hashCode for an array handling multi-dimensional arrays correctly.</p>
     * 
     * <p>Multi-dimensional primitive arrays are also handled correctly by this method.</p>
     * 
     * @param array  the array to get a hashCode for, may be <code>null</code>
     * @return a hashCode for the array, zero if null array input
     */
    public static int hashCode(final Object array) {
        return new HashCodeBuilder().append(array).toHashCode();
    }

    /**
     * <p>Compares two arrays, using equals(), handling multi-dimensional arrays
     * correctly.</p>
     * 
     * <p>Multi-dimensional primitive arrays are also handled correctly by this method.</p>
     * 
     * @param array1  the array to get a hashCode for, may be <code>null</code>
     * @param array2  the array to get a hashCode for, may be <code>null</code>
     * @return <code>true</code> if the arrays are equal
     */
    public static boolean isEquals(final Object array1, final Object array2) {
        return new EqualsBuilder().append(array1, array2).isEquals();
    }

    // To map
    //-----------------------------------------------------------------------
    /**
     * <p>Converts the given array into a {@link java.util.Map}. Each element of the array
     * must be either a {@link java.util.Map.Entry} or an Array, containing at least two
     * elements, where the first element is used as key and the second as
     * value.</p>
     *
     * <p>This method can be used to initialize:</p>
     * <pre>
     * // Create a Map mapping colors.
     * Map colorMap = MapUtils.toMap(new String[][] {{
     *     {"RED", "#FF0000"},
     *     {"GREEN", "#00FF00"},
     *     {"BLUE", "#0000FF"}});
     * </pre>
     * 
     * <p>This method returns <code>null</code> if <code>null</code> array input.</p>
     *
     * @param array  an array whose elements are either a {@link java.util.Map.Entry} or 
     *  an Array containing at least two elements, may be <code>null</code>
     * @return a <code>Map</code> that was created from the array
     * @throws IllegalArgumentException  if one element of this Array is
     *  itself an Array containing less then two elements
     * @throws IllegalArgumentException  if the array contains elements other
     *  than {@link java.util.Map.Entry} and an Array
     */
    public static Map toMap(final Object[] array) {
        if (array == null) {
            return null;
        }
        final Map map = new HashMap((int) (array.length * 1.5));
        for (int i = 0; i < array.length; i++) {
            Object object = array[i];
            if (object instanceof Map.Entry) {
                Map.Entry entry = (Map.Entry) object;
                map.put(entry.getKey(), entry.getValue());
            } else if (object instanceof Object[]) {
                Object[] entry = (Object[]) object;
                if (entry.length < 2) {
                    throw new IllegalArgumentException("Array element " + i + ", '" 
                        + object
                        + "', has a length less than 2");
                }
                map.put(entry[0], entry[1]);
            } else {
                throw new IllegalArgumentException("Array element " + i + ", '" 
                        + object
                        + "', is neither of type Map.Entry nor an Array");
            }
        }
        return map;
    }

    // Clone
    //-----------------------------------------------------------------------
    /**
     * <p>Shallow clones an array returning a typecast result and handling
     * <code>null</code>.</p>
     *
     * <p>The objecs in the array are not cloned, thus there is no special
     * handling for multi-dimensional arrays.</p>
     * 
     * <p>This method returns <code>null</code> if <code>null</code> array input.</p>
     * 
     * @param array  the array to shallow clone, may be <code>null</code>
     * @return the cloned array, <code>null</code> if <code>null</code> input
     */
    public static Object[] clone(final Object[] array) {
        if (array == null) {
            return null;
        }
        return (Object[]) array.clone();
    }

    /**
     * <p>Clones an array returning a typecast result and handling
     * <code>null</code>.</p>
     *
     * <p>This method returns <code>null</code> if <code>null</code> array input.</p>
     * 
     * @param array  the array to clone, may be <code>null</code>
     * @return the cloned array, <code>null</code> if <code>null</code> input
     */
    public static long[] clone(final long[] array) {
        if (array == null) {
            return null;
        }
        return (long[]) array.clone();
    }

    /**
     * <p>Clones an array returning a typecast result and handling
     * <code>null</code>.</p>
     *
     * <p>This method returns <code>null</code> if <code>null</code> array input.</p>
     * 
     * @param array  the array to clone, may be <code>null</code>
     * @return the cloned array, <code>null</code> if <code>null</code> input
     */
    public static int[] clone(int[] array) {
        if (array == null) {
            return null;