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</code> instead of a <code>Vector</code>, so it is not
025 * synchronized to protect against multi-threaded 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</code> 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 * Unlike <code>Stack</code>, <code>ArrayStack</code> accepts null entries.
035 * <p>
036 * <b>Note:</b> From version 4.0 onwards, this class does not implement the
037 * removed {@code Buffer} interface anymore.
038 *
039 * @param <E> the type of elements in this list
040 * @see java.util.Stack
041 * @since 1.0
042 * @deprecated use {@link java.util.ArrayDeque} instead (available from Java 1.6)
043 */
044@Deprecated
045public class ArrayStack<E> extends ArrayList<E> {
046
047    /** Ensure serialization compatibility */
048    private static final long serialVersionUID = 2130079159931574599L;
049
050    /**
051     * Constructs a new empty <code>ArrayStack</code>. The initial size
052     * is controlled by <code>ArrayList</code> and is currently 10.
053     */
054    public ArrayStack() {
055        super();
056    }
057
058    /**
059     * Constructs a new empty <code>ArrayStack</code> with an initial size.
060     *
061     * @param initialSize  the initial size to use
062     * @throws IllegalArgumentException  if the specified initial size
063     *  is negative
064     */
065    public ArrayStack(final int initialSize) {
066        super(initialSize);
067    }
068
069    /**
070     * Return <code>true</code> if this stack is currently empty.
071     * <p>
072     * This method exists for compatibility with <code>java.util.Stack</code>.
073     * New users of this class should use <code>isEmpty</code> instead.
074     *
075     * @return true if the stack is currently empty
076     */
077    public boolean empty() {
078        return isEmpty();
079    }
080
081    /**
082     * Returns the top item off of this stack without removing it.
083     *
084     * @return the top item on the stack
085     * @throws EmptyStackException  if the stack is empty
086     */
087    public E peek() throws EmptyStackException {
088        final int n = size();
089        if (n <= 0) {
090            throw new EmptyStackException();
091        }
092        return get(n - 1);
093    }
094
095    /**
096     * Returns the n'th item down (zero-relative) from the top of this
097     * stack without removing it.
098     *
099     * @param n  the number of items down to go
100     * @return the n'th item on the stack, zero relative
101     * @throws EmptyStackException  if there are not enough items on the
102     *  stack to satisfy this request
103     */
104    public E peek(final int n) throws EmptyStackException {
105        final int m = (size() - n) - 1;
106        if (m < 0) {
107            throw new EmptyStackException();
108        }
109        return get(m);
110    }
111
112    /**
113     * Pops the top item off of this stack and return it.
114     *
115     * @return the top item on the stack
116     * @throws EmptyStackException  if the stack is empty
117     */
118    public E pop() throws EmptyStackException {
119        final int n = size();
120        if (n <= 0) {
121            throw new EmptyStackException();
122        }
123        return remove(n - 1);
124    }
125
126    /**
127     * Pushes a new item onto the top of this stack. The pushed item is also
128     * returned. This is equivalent to calling <code>add</code>.
129     *
130     * @param item  the item to be added
131     * @return the item just pushed
132     */
133    public E push(final E item) {
134        add(item);
135        return item;
136    }
137
138    /**
139     * Returns the one-based position of the distance from the top that the
140     * specified object exists on this stack, where the top-most element is
141     * considered to be at distance <code>1</code>.  If the object is not
142     * present on the stack, return <code>-1</code> instead.  The
143     * <code>equals()</code> method is used to compare to the items
144     * in this stack.
145     *
146     * @param object  the object to be searched for
147     * @return the 1-based depth into the stack of the object, or -1 if not found
148     */
149    public int search(final Object object) {
150        int i = size() - 1;        // Current index
151        int n = 1;                 // Current distance
152        while (i >= 0) {
153            final Object current = get(i);
154            if ((object == null && current == null) ||
155                (object != null && object.equals(current))) {
156                return n;
157            }
158            i--;
159            n++;
160        }
161        return -1;
162    }
163
164}