ArrayListStack.java Source code

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Here is the source code for ArrayListStack.java

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/*
 * 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.
 */

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

/**
 * A faster, smaller stack implementation. ArrayListStack is final and unsynchronized (the JDK's
 * methods are synchronized). In addition you can set the initial capacity if you want via the
 * ArrayListStack(int) constructor.
 * 
 * @author Jonathan Locke
 * @param <T>
 */
public final class ArrayListStack<T> extends ArrayList<T> {
    private static final long serialVersionUID = 1L;

    /**
     * Construct.
     * 
     * @param initialCapacity
     *            Initial capacity of the stack
     */
    public ArrayListStack(final int initialCapacity) {
        super(initialCapacity);
    }

    /**
     * Construct.
     */
    public ArrayListStack() {
        this(10);
    }

    /**
     * Construct.
     * 
     * @param collection
     *            The collection to add
     */
    public ArrayListStack(final Collection<T> collection) {
        super(collection);
    }

    /**
     * Pushes an item onto the top of this stack.
     * 
     * @param item
     *            the item to be pushed onto this stack.
     */
    public final void push(final T item) {
        add(item);
    }

    /**
     * Removes the object at the top of this stack and returns that object.
     * 
     * @return The object at the top of this stack
     * @exception EmptyStackException
     *                If this stack is empty.
     */
    public final T pop() {
        final T top = peek();
        remove(size() - 1);
        return top;
    }

    /**
     * Looks at the object at the top of this stack without removing it.
     * 
     * @return The object at the top of this stack
     * @exception EmptyStackException
     *                If this stack is empty.
     */
    public final T peek() {
        int size = size();
        if (size == 0) {
            throw new EmptyStackException();
        }
        return get(size - 1);
    }

    /**
     * Tests if this stack is empty.
     * 
     * @return <code>true</code> if and only if this stack contains no items; <code>false</code>
     *         otherwise.
     */
    public final boolean empty() {
        return size() == 0;
    }

    /**
     * Returns the 1-based position where an object is on this stack. If the object <tt>o</tt>
     * occurs as an item in this stack, this method returns the distance from the top of the stack
     * of the occurrence nearest the top of the stack; the topmost item on the stack is considered
     * to be at distance <tt>1</tt>. The <tt>equals</tt> method is used to compare <tt>o</tt>
     * to the items in this stack.
     * 
     * @param o
     *            the desired object.
     * @return the 1-based position from the top of the stack where the object is located; the
     *         return value <code>-1</code> indicates that the object is not on the stack.
     */
    public final int search(final T o) {
        int i = lastIndexOf(o);
        if (i >= 0) {
            return size() - i;
        }
        return -1;
    }
}