    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}