ArrayHelper.java Source code

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Here is the source code for ArrayHelper.java

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/*
 * Convenience methods for working with Java arrays.
 * Copyright (C) 2005 Stephen Ostermiller
 * http://ostermiller.org/contact.pl?regarding=Java+Utilities
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * See COPYING.TXT for details.
 */

import java.io.IOException;
import java.lang.reflect.Array;

/**
 * Convenience methods for working with Java arrays.
 * More information about this class is available from <a target="_top" href=
 * "http://ostermiller.org/utils/ArrayHelper.html">ostermiller.org</a>.
 *
 * @author Stephen Ostermiller http://ostermiller.org/contact.pl?regarding=Java+Utilities
 * @since ostermillerutils 1.06.00
 */
public final class ArrayHelper {

    /**
     * Concatenates the given arrays into a single long array.
     * The returned array will be of the common super type of the
     * two given arrays.
     * <p>
     * For example it can be called like this:<br>
     * <pre>
     * String[] arr = (String[])ArrayHelper.cat(new String[]{"one","two"}, new String[]{"three","four"});
     * </pre>
     *
     * @param arr1 first array
     * @param arr2 second array
     * @return an array whose length is the sum of the given array's lengths and contains all the elements in the given arrays.
     * @since ostermillerutils 1.06.00
     */
    public static Object[] cat(Object[] arr1, Object[] arr2) {
        // Use reflection to find the super class of both arrays
        Class<?> commonSuperClass = Object.class;
        boolean foundcommonSuperClass = false;
        for (Class<?> c1 = arr1.getClass().getComponentType(); !foundcommonSuperClass
                && !c1.equals(Object.class); c1 = c1.getSuperclass()) {
            for (Class<?> c2 = arr2.getClass().getComponentType(); !foundcommonSuperClass
                    && !c2.equals(Object.class); c2 = c2.getSuperclass()) {
                if (c2.equals(c1)) {
                    foundcommonSuperClass = true;
                    commonSuperClass = c1;
                }
            }
        }
        // Create a new array of the correct type
        Object[] result = (Object[]) Array.newInstance(commonSuperClass, arr1.length + arr2.length);
        // Copy the two arrays into the large array
        System.arraycopy(arr1, 0, result, 0, arr1.length);
        System.arraycopy(arr2, 0, result, arr1.length, arr2.length);
        return result;
    }

    /**
     * Tests two arrays to see if the arrays are equal.
     * Two arrays will be equal only if they are the same length
     * and contain objects that are equal in the same order.
     *
     * @param arr1 first array
     * @param arr2 second array
     * @return true iff two arguments are equal
     * @since ostermillerutils 1.06.00
     */
    public static boolean equal(Object[] arr1, Object[] arr2) {
        if (arr1 == null && arr2 == null)
            return true;
        if (arr1 == null || arr2 == null)
            return false;
        if (arr1.length != arr2.length)
            return false;
        for (int i = 0; i < arr1.length; i++) {
            if (!equalObjects(arr1[i], arr2[i]))
                return false;
        }
        return true;
    }

    /**
     * Tests if the two objects are equal
     *
     * @param o1 first object
     * @param o2 second object
     * @since ostermillerutils 1.06.00
     */
    private static boolean equalObjects(Object o1, Object o2) {
        if (o1 == null && o2 == null)
            return true;
        if (o1 == null || o2 == null)
            return false;
        return o1.equals(o2);
    }
}