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/**
 * Copyright (C) 2009 Authors
 * 
 * This file is part of Ebean.
 * 
 * Ebean is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *  
 * Ebean is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with Ebean; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA  
 */
package com.avaje.ebeaninternal.server.util;

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

/**
 * Stack based on ArrayList.
 *
 * @author rbygrave
 */
public class ArrayStack {

    private final ArrayList list;

    /**
     * Creates an empty Stack with an initial size.
     */
    public ArrayStack(int size) {
        this.list = new ArrayList(size);
    }

    /**
     * Creates an empty Stack.
     */
    public ArrayStack() {
        this.list = new ArrayList();
    }

    /**
     * Pushes an item onto the top of this stack. 
     */
    public E push(E item) {
        list.add(item);
        return item;
    }

    /**
     * Removes the object at the top of this stack and returns that object as
     * the value of this function.
     */
    public E pop() {
        int len = list.size();
        E obj = peek();
        list.remove(len - 1);
        return obj;
    }

    protected E peekZero(boolean retNull) {
        int len = list.size();
        if (len == 0) {
            if (retNull) {
                return null;
            }
            throw new EmptyStackException();
        }
        return list.get(len - 1);
    }

    /**
     * Returns the object at the top of this stack without removing it.
     */
    public E peek() {
        return peekZero(false);
    }
    
    /**
     * Returns the object at the top of this stack without removing it.
     * If the stack is empty this returns null.
     */
    public E peekWithNull() {
        return peekZero(true);
    }
    
    /**
     * Tests if this stack is empty.
     */
    public boolean isEmpty() {
        return list.isEmpty();
    }

    public int size(){
        return list.size();
    }
}