Main.java Source code

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/*   Copyright 2004 The Apache Software Foundation
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *  limitations under the License.
 */

import java.lang.reflect.Array;

/**
 * <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:fredrik@westermarck.com">Fredrik Westermarck</a>
 * @author Nikolay Metchev
 * @author Matthew Hawthorne
 * @author Tim O'Brien
 * @author Pete Gieser
 * @author Gary Gregory
 * @author <a href="mailto:equinus100@hotmail.com">Ashwin S</a>
 * @author Maarten Coene
 * @since 2.0
 * @version $Id: ArrayUtils.java 632503 2008-03-01 00:21:52Z ggregory $
 */
public class Main {

    /**
     * <p>Removes the first occurrence of the specified element from the
     * specified array. All subsequent elements are shifted to the left 
     * (substracts one from their indices). If the array doesn't contains
     * such an element, no elements are removed from the array.</p>
     *
     * <p>This method returns a new array with the same elements of the input
     * array except the first occurrence of the specified element. The component 
     * type of the returned array is always the same as that of the input 
     * array.</p>
     *
     * <pre>
     * ArrayUtils.removeElement(null, 1)      = null
     * ArrayUtils.removeElement([], 1)        = []
     * ArrayUtils.removeElement([1], 2)       = [1]
     * ArrayUtils.removeElement([1, 3], 1)    = [3]
     * ArrayUtils.removeElement([1, 3, 1], 1) = [3, 1]
     * </pre>
     * 
     * @param array  the array to remove the element from, may be <code>null</code>
     * @param element  the element to be removed
     * @return A new array containing the existing elements except the first
     *         occurrence of the specified element.
     * @since 2.1
     */
    public static short[] removeElement(short[] array, short element) {
        int index = indexOf(array, element);
        if (index == -1) {
            return clone(array);
        }
        return remove(array, index);
    }

    /**
     * <p>Removes the element at the specified position from the specified array.
     * All subsequent elements are shifted to the left (substracts one from
     * their indices).</p>
     *
     * <p>This method returns a new array with the same elements of the input
     * array except the element on the specified position. The component 
     * type of the returned array is always the same as that of the input 
     * array.</p>
     *
     * <p>If the input array is <code>null</code>, an IndexOutOfBoundsException
     * will be thrown, because in that case no valid index can be specified.</p>
     *
     * <pre>
     * ArrayUtils.remove([1], 0)         = []
     * ArrayUtils.remove([2, 6], 0)      = [6]
     * ArrayUtils.remove([2, 6], 1)      = [2]
     * ArrayUtils.remove([2, 6, 3], 1)   = [2, 3]
     * </pre>
     * 
     * @param array  the array to remove the element from, may not be <code>null</code>
     * @param index  the position of the element to be removed
     * @return A new array containing the existing elements except the element
     *         at the specified position.
     * @throws IndexOutOfBoundsException if the index is out of range 
     * (index < 0 || index >= array.length), or if the array is <code>null</code>.
     * @since 2.1
     */
    public static short[] remove(short[] array, int index) {
        return (short[]) remove((Object) array, index);
    }

    /**
     * <p>Removes the element at the specified position from the specified array.
     * All subsequent elements are shifted to the left (substracts one from
     * their indices).</p>
     *
     * <p>This method returns a new array with the same elements of the input
     * array except the element on the specified position. The component 
     * type of the returned array is always the same as that of the input 
     * array.</p>
     *
     * <p>If the input array is <code>null</code>, an IndexOutOfBoundsException
     * will be thrown, because in that case no valid index can be specified.</p>
     * 
     * @param array  the array to remove the element from, may not be <code>null</code>
     * @param index  the position of the element to be removed
     * @return A new array containing the existing elements except the element
     *         at the specified position.
     * @throws IndexOutOfBoundsException if the index is out of range 
     * (index < 0 || index >= array.length), or if the array is <code>null</code>.
     * @since 2.1
     */
    private static Object remove(Object array, int index) {
        int length = getLength(array);
        if (index < 0 || index >= length) {
            throw new IndexOutOfBoundsException("Index: " + index + ", Length: " + length);
        }

        Object result = Array.newInstance(array.getClass().getComponentType(), length - 1);
        System.arraycopy(array, 0, result, 0, index);
        if (index < length - 1) {
            System.arraycopy(array, index + 1, result, index, length - index - 1);
        }

        return result;
    }

    /**
     * <p>Finds the index of the given value in the array starting at the given index.</p>
     *
     * <p>This method returns {@link #INDEX_NOT_FOUND} (<code>-1</code>) for a <code>null</code> input array.</p>
     *
     * <p>A negative startIndex is treated as zero. A startIndex larger than the array
     * length will return {@link #INDEX_NOT_FOUND} (<code>-1</code>).</p>
     * 
     * @param array  the array to search through for the object, may be <code>null</code>
     * @param valueToFind  the value to find
     * @param startIndex  the index to start searching at
     * @return the index of the value within the array,
     *  {@link #INDEX_NOT_FOUND} (<code>-1</code>) if not found or <code>null</code> array input
     */
    public static int indexOf(short[] array, short valueToFind) {
        if (array == null) {
            return -1;
        }
        for (int i = 0; i < array.length; i++) {
            if (valueToFind == array[i]) {
                return i;
            }
        }
        return -1;
    }

    /**
     * <p>Returns the length of the specified array.
     * This method can deal with <code>Object</code> arrays and with primitive arrays.</p>
     *
     * <p>If the input array is <code>null</code>, <code>0</code> is returned.</p>
     *
     * <pre>
     * ArrayUtils.getLength(null)            = 0
     * ArrayUtils.getLength([])              = 0
     * ArrayUtils.getLength([null])          = 1
     * ArrayUtils.getLength([true, false])   = 2
     * ArrayUtils.getLength([1, 2, 3])       = 3
     * ArrayUtils.getLength(["a", "b", "c"]) = 3
     * </pre>
     *
     * @param array  the array to retrieve the length from, may be null
     * @return The length of the array, or <code>0</code> if the array is <code>null</code>
     * @throws IllegalArgumentException if the object arguement is not an array.
     * @since 2.1
     */
    public static int getLength(Object array) {
        if (array == null) {
            return 0;
        }
        return Array.getLength(array);
    }

    /**
     * <p>Shallow clones an array returning a typecast result and handling
     * <code>null</code>.</p>
     *
     * <p>The objects in the array are not cloned, thus there is no special
     * handling for multi-dimensional arrays.</p>
     * 
     * <p>This method returns <code>null</code> for a <code>null</code> input array.</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 short[] clone(short[] array) {
        if (array == null) {
            return null;
        }
        return (short[]) array.clone();
    }

}