001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.collections4; 018 019import java.util.ArrayList; 020import java.util.EmptyStackException; 021 022/** 023 * An implementation of the {@link java.util.Stack} API that is based on an 024 * {@code ArrayList} instead of a {@code Vector}, so it is not 025 * synchronized to protect against multithreaded access. The implementation 026 * is therefore operates faster in environments where you do not need to 027 * worry about multiple thread contention. 028 * <p> 029 * The removal order of an {@code ArrayStack} is based on insertion 030 * order: The most recently added element is removed first. The iteration 031 * order is <i>not</i> the same as the removal order. The iterator returns 032 * elements from the bottom up. 033 * </p> 034 * <p> 035 * Unlike {@code Stack}, {@code ArrayStack} accepts null entries. 036 * <p> 037 * <b>Note:</b> From version 4.0 onwards, this class does not implement the 038 * removed {@code Buffer} interface anymore. 039 * </p> 040 * 041 * @param <E> the type of elements in this list 042 * @see java.util.Stack 043 * @since 1.0 044 * @deprecated use {@link java.util.ArrayDeque} instead (available from Java 1.6) 045 */ 046@Deprecated 047public class ArrayStack<E> extends ArrayList<E> { 048 049 /** Ensure serialization compatibility */ 050 private static final long serialVersionUID = 2130079159931574599L; 051 052 /** 053 * Constructs a new empty {@code ArrayStack}. The initial size 054 * is controlled by {@code ArrayList} and is currently 10. 055 */ 056 public ArrayStack() { 057 } 058 059 /** 060 * Constructs a new empty {@code ArrayStack} with an initial size. 061 * 062 * @param initialSize the initial size to use 063 * @throws IllegalArgumentException if the specified initial size 064 * is negative 065 */ 066 public ArrayStack(final int initialSize) { 067 super(initialSize); 068 } 069 070 /** 071 * Return {@code true} if this stack is currently empty. 072 * <p> 073 * This method exists for compatibility with {@link java.util.Stack}. 074 * New users of this class should use {@code isEmpty} instead. 075 * 076 * @return true if the stack is currently empty 077 */ 078 public boolean empty() { 079 return isEmpty(); 080 } 081 082 /** 083 * Returns the top item off of this stack without removing it. 084 * 085 * @return the top item on the stack 086 * @throws EmptyStackException if the stack is empty 087 */ 088 public E peek() throws EmptyStackException { 089 final int n = size(); 090 if (n <= 0) { 091 throw new EmptyStackException(); 092 } 093 return get(n - 1); 094 } 095 096 /** 097 * Returns the n'th item down (zero-relative) from the top of this 098 * stack without removing it. 099 * 100 * @param n the number of items down to go 101 * @return the n'th item on the stack, zero relative 102 * @throws EmptyStackException if there are not enough items on the 103 * stack to satisfy this request 104 */ 105 public E peek(final int n) throws EmptyStackException { 106 final int m = size() - n - 1; 107 if (m < 0) { 108 throw new EmptyStackException(); 109 } 110 return get(m); 111 } 112 113 /** 114 * Pops the top item off of this stack and return it. 115 * 116 * @return the top item on the stack 117 * @throws EmptyStackException if the stack is empty 118 */ 119 public E pop() throws EmptyStackException { 120 final int n = size(); 121 if (n <= 0) { 122 throw new EmptyStackException(); 123 } 124 return remove(n - 1); 125 } 126 127 /** 128 * Pushes a new item onto the top of this stack. The pushed item is also 129 * returned. This is equivalent to calling {@code add}. 130 * 131 * @param item the item to be added 132 * @return the item just pushed 133 */ 134 public E push(final E item) { 135 add(item); 136 return item; 137 } 138 139 /** 140 * Returns the one-based position of the distance from the top that the 141 * specified object exists on this stack, where the top-most element is 142 * considered to be at distance {@code 1}. If the object is not 143 * present on the stack, return {@code -1} instead. The 144 * {@code equals()} method is used to compare to the items 145 * in this stack. 146 * 147 * @param object the object to be searched for 148 * @return the 1-based depth into the stack of the object, or -1 if not found 149 */ 150 public int search(final Object object) { 151 int i = size() - 1; // Current index 152 int n = 1; // Current distance 153 while (i >= 0) { 154 final Object current = get(i); 155 if (object == null && current == null || 156 object != null && object.equals(current)) { 157 return n; 158 } 159 i--; 160 n++; 161 } 162 return -1; 163 } 164 165}