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Commons Collections example source code file (ArrayStack.java)

This example Commons Collections source code file (ArrayStack.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

arraylist, arraystack, arraystack, buffer, bufferunderflowexception, current, current, emptystackexception, emptystackexception, object, object, util

The Commons Collections ArrayStack.java source code

/*
 *  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.commons.collections;

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

/**
 * An implementation of the {@link java.util.Stack} API that is based on an
 * <code>ArrayList instead of a Vector, 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 is based on insertion 
 * order: The most recently added element is removed first.  The iteration
 * order is <i>not 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, ArrayStack accepts null entries.
 *
 * @see java.util.Stack
 * @since Commons Collections 1.0
 * @version $Revision: 646777 $ $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 extends ArrayList implements Buffer {

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

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

    /**
     * Constructs a new empty <code>ArrayStack 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 if this stack is currently empty.
     * <p>
     * This method exists for compatibility with <code>java.util.Stack.
     * New users of this class should use <code>isEmpty 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 Object peek() throws EmptyStackException {
        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 Object peek(int n) throws EmptyStackException {
        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 Object pop() throws EmptyStackException {
        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.
     *
     * @param item  the item to be added
     * @return the item just pushed
     */
    public Object push(Object 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.  If the object is not
     * present on the stack, return <code>-1 instead.  The
     * <code>equals() 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(Object 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;
    }

    /**
     * Returns the element on the top of the stack.
     *
     * @return the element on the top of the stack
     * @throws BufferUnderflowException  if the stack is empty
     */
    public Object get() {
        int size = size();
        if (size == 0) {
            throw new BufferUnderflowException();
        }
        return get(size - 1);
    }

    /**
     * Removes the element on the top of the stack.
     *
     * @return the removed element 
     * @throws BufferUnderflowException  if the stack is empty
     */
    public Object remove() {
        int size = size();
        if (size == 0) {
            throw new BufferUnderflowException();
        }
        return remove(size - 1);
    }

}

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