1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4;
18
19 import java.util.ArrayList;
20 import java.util.EmptyStackException;
21
22 /**
23 * An implementation of the {@link java.util.Stack} API that is based on an
24 * {@code ArrayList} instead of a {@code Vector}, so it is not
25 * synchronized to protect against multithreaded access. The implementation
26 * is therefore operates faster in environments where you do not need to
27 * worry about multiple thread contention.
28 * <p>
29 * The removal order of an {@code ArrayStack} is based on insertion
30 * order: The most recently added element is removed first. The iteration
31 * order is <i>not</i> the same as the removal order. The iterator returns
32 * elements from the bottom up.
33 * </p>
34 * <p>
35 * Unlike {@code Stack}, {@code ArrayStack} accepts null entries.
36 * <p>
37 * <b>Note:</b> From version 4.0 onwards, this class does not implement the
38 * removed {@code Buffer} interface anymore.
39 * </p>
40 *
41 * @param <E> the type of elements in this list
42 * @see java.util.Stack
43 * @since 1.0
44 * @deprecated use {@link java.util.ArrayDeque} instead (available from Java 1.6)
45 */
46 @Deprecated
47 public class ArrayStack<E> extends ArrayList<E> {
48
49 /** Ensure serialization compatibility */
50 private static final long serialVersionUID = 2130079159931574599L;
51
52 /**
53 * Constructs a new empty {@code ArrayStack}. The initial size
54 * is controlled by {@code ArrayList} and is currently 10.
55 */
56 public ArrayStack() {
57 }
58
59 /**
60 * Constructs a new empty {@code ArrayStack} with an initial size.
61 *
62 * @param initialSize the initial size to use
63 * @throws IllegalArgumentException if the specified initial size
64 * is negative
65 */
66 public ArrayStack(final int initialSize) {
67 super(initialSize);
68 }
69
70 /**
71 * Return {@code true} if this stack is currently empty.
72 * <p>
73 * This method exists for compatibility with {@link java.util.Stack}.
74 * New users of this class should use {@code isEmpty} instead.
75 *
76 * @return true if the stack is currently empty
77 */
78 public boolean empty() {
79 return isEmpty();
80 }
81
82 /**
83 * Returns the top item off of this stack without removing it.
84 *
85 * @return the top item on the stack
86 * @throws EmptyStackException if the stack is empty
87 */
88 public E peek() throws EmptyStackException {
89 final int n = size();
90 if (n <= 0) {
91 throw new EmptyStackException();
92 }
93 return get(n - 1);
94 }
95
96 /**
97 * Returns the n'th item down (zero-relative) from the top of this
98 * stack without removing it.
99 *
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 }