Java tutorial
/* 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(); } }