Java tutorial
//package com.java2s; /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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; public class Main { /** * The index value when an element is not found in a list or array: <code>-1</code>. * This value is returned by methods in this class and can also be used in comparisons with values returned by * various method from {@link java.util.List}. */ public static final int INDEX_NOT_FOUND = -1; /** * <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/> * <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> * <p/> * <pre> * ArrayUtils.removeElement(null, "a") = null * ArrayUtils.removeElement([], "a") = [] * ArrayUtils.removeElement(["a"], "b") = ["a"] * ArrayUtils.removeElement(["a", "b"], "a") = ["b"] * ArrayUtils.removeElement(["a", "b", "a"], "a") = ["b", "a"] * </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 Object[] removeElement(Object[] array, Object element) { int index = indexOf(array, element); if (index == INDEX_NOT_FOUND) { return clone(array); } return remove(array, index); } /** * <p>Finds the index of the given object in the array.</p> * <p/> * <p>This method returns {@link #INDEX_NOT_FOUND} (<code>-1</code>) for a <code>null</code> input array.</p> * * @param array the array to search through for the object, may be <code>null</code> * @param objectToFind the object to find, may be <code>null</code> * @return the index of the object within the array, * {@link #INDEX_NOT_FOUND} (<code>-1</code>) if not found or <code>null</code> array input */ public static int indexOf(Object[] array, Object objectToFind) { return indexOf(array, objectToFind, 0); } /** * <p>Finds the index of the given object in the array starting at the given index.</p> * <p/> * <p>This method returns {@link #INDEX_NOT_FOUND} (<code>-1</code>) for a <code>null</code> input array.</p> * <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 objectToFind the object to find, may be <code>null</code> * @param startIndex the index to start searching at * @return the index of the object within the array starting at the index, * {@link #INDEX_NOT_FOUND} (<code>-1</code>) if not found or <code>null</code> array input */ public static int indexOf(Object[] array, Object objectToFind, int startIndex) { if (array == null) { return INDEX_NOT_FOUND; } if (startIndex < 0) { startIndex = 0; } if (objectToFind == null) { for (int i = startIndex; i < array.length; i++) { if (array[i] == null) { return i; } } } else { for (int i = startIndex; i < array.length; i++) { if (objectToFind.equals(array[i])) { return i; } } } return INDEX_NOT_FOUND; } /** * <p>Finds the index of the given value in the array.</p> * <p/> * <p>This method returns {@link #INDEX_NOT_FOUND} (<code>-1</code>) for a <code>null</code> input array.</p> * * @param array the array to search through for the object, may be <code>null</code> * @param valueToFind the value to find * @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 * @since 2.1 */ public static int indexOf(char[] array, char valueToFind) { return indexOf(array, valueToFind, 0); } /** * <p>Finds the index of the given value in the array starting at the given index.</p> * <p/> * <p>This method returns {@link #INDEX_NOT_FOUND} (<code>-1</code>) for a <code>null</code> input array.</p> * <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 * @since 2.1 */ public static int indexOf(char[] array, char valueToFind, int startIndex) { if (array == null) { return INDEX_NOT_FOUND; } if (startIndex < 0) { startIndex = 0; } for (int i = startIndex; i < array.length; i++) { if (valueToFind == array[i]) { return i; } } return INDEX_NOT_FOUND; } /** * <p>Shallow clones an array returning a typecast result and handling * <code>null</code>.</p> * <p/> * <p>The objects in the array are not cloned, thus there is no special * handling for multi-dimensional arrays.</p> * <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 Object[] clone(Object[] array) { if (array == null) { return null; } return (Object[]) array.clone(); } /** * <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/> * <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/> * <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> * <p/> * <pre> * ArrayUtils.remove(["a"], 0) = [] * ArrayUtils.remove(["a", "b"], 0) = ["b"] * ArrayUtils.remove(["a", "b"], 1) = ["a"] * ArrayUtils.remove(["a", "b", "c"], 1) = ["a", "c"] * </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 Object[] remove(Object[] array, int index) { return (Object[]) 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/> * <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/> * <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>Returns the length of the specified array. * This method can deal with <code>Object</code> arrays and with primitive arrays.</p> * <p/> * <p>If the input array is <code>null</code>, <code>0</code> is returned.</p> * <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); } }