tiles-api/src/main/java/org/apache/tiles/ArrayStack.java

/*
 * $Id$
 *
 * 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.
 */

package org.apache.tiles;

import java.util.ArrayList;
import java.util.EmptyStackException;

/**
 * This class has been copied from Apache Commons Collections 3.2.1 and adapted
 * to Java 5 generics. Here follows the original comment.<br>
 *
 * An implementation of the {@link java.util.Stack} API that is based on an
 * <code>ArrayList</code> instead of a <code>Vector</code>, so it is not
 * synchronized to protect against multi-threaded access. The implementation is
 * therefore operates faster in environments where you do not need to worry
 * about multiple thread contention.
 * <p>
 * The removal order of an <code>ArrayStack</code> is based on insertion order:
 * The most recently added element is removed first. The iteration order is
 * <i>not</i> the same as the removal order. The iterator returns elements from
 * the bottom up, whereas the {@link #remove()} method removes them from the top
 * down.
 * <p>
 * Unlike <code>Stack</code>, <code>ArrayStack</code> accepts null entries.
 *
 * @param <T> The type of the element of the stack.
 * @see java.util.Stack
 * @since Commons Collections 1.0
 * @version $Revision$ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr
 * 2008) $
 *
 * @author Craig R. McClanahan
 * @author Paul Jack
 * @author Stephen Colebourne
 */
public class ArrayStack<T> extends ArrayList<T> {

    /** Ensure serialization compatibility. */
    private static final long serialVersionUID = 2130079159931574599L;

    /**
     * Constructs a new empty <code>ArrayStack</code>. The initial size
     * is controlled by <code>ArrayList</code> and is currently 10.
     */
    public ArrayStack() {
        super();
    }

    /**
     * Constructs a new empty <code>ArrayStack</code> with an initial size.
     *
     * @param initialSize  the initial size to use
     * @throws IllegalArgumentException  if the specified initial size
     *  is negative
     */
    public ArrayStack(int initialSize) {
        super(initialSize);
    }

    /**
     * Return <code>true</code> if this stack is currently empty.
     * <p>
     * This method exists for compatibility with <code>java.util.Stack</code>.
     * New users of this class should use <code>isEmpty</code> instead.
     *
     * @return true if the stack is currently empty
     */
    public boolean empty() {
        return isEmpty();
    }

    /**
     * Returns the top item off of this stack without removing it.
     *
     * @return the top item on the stack
     * @throws EmptyStackException  if the stack is empty
     */
    public T peek() {
        int n = size();
        if (n <= 0) {
            throw new EmptyStackException();
        } else {
            return get(n - 1);
        }
    }

    /**
     * Returns the n'th item down (zero-relative) from the top of this
     * stack without removing it.
     *
     * @param n  the number of items down to go
     * @return the n'th item on the stack, zero relative
     * @throws EmptyStackException  if there are not enough items on the
     *  stack to satisfy this request
     */
    public T peek(int n) {
        int m = (size() - n) - 1;
        if (m < 0) {
            throw new EmptyStackException();
        } else {
            return get(m);
        }
    }

    /**
     * Pops the top item off of this stack and return it.
     *
     * @return the top item on the stack
     * @throws EmptyStackException  if the stack is empty
     */
    public T pop() {
        int n = size();
        if (n <= 0) {
            throw new EmptyStackException();
        } else {
            return remove(n - 1);
        }
    }

    /**
     * Pushes a new item onto the top of this stack. The pushed item is also
     * returned. This is equivalent to calling <code>add</code>.
     *
     * @param item  the item to be added
     * @return the item just pushed
     */
    public T push(T item) {
        add(item);
        return item;
    }

    /**
     * Returns the one-based position of the distance from the top that the
     * specified object exists on this stack, where the top-most element is
     * considered to be at distance <code>1</code>.  If the object is not
     * present on the stack, return <code>-1</code> instead.  The
     * <code>equals()</code> method is used to compare to the items
     * in this stack.
     *
     * @param object  the object to be searched for
     * @return the 1-based depth into the stack of the object, or -1 if not found
     */
    public int search(T object) {
        int i = size() - 1;        // Current index
        int n = 1;                 // Current distance
        while (i >= 0) {
            Object current = get(i);
            if ((object == null && current == null)
                    || (object != null && object.equals(current))) {
                return n;
            }
            i--;
            n++;
        }
        return -1;
    }
}