stack2.java

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/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 

import java.util.*;

public class Stack2<T> implements Cloneable {
    private ArrayList<T> items;
    private int top=0;

    public Stack2() {
        items = new ArrayList<T>();
    }

    public void push(T item) {
         items.add(item);
         top++;
    }

    public T pop() {
      if (items.size() == 0)
          throw new EmptyStackException();
      T obj = items.get(--top);
      return obj;
    }

    public boolean isEmpty() {
      if (items.size() == 0)
         return true;
      else
         return false;
    }

    protected Stack2<T> clone() {
      try {
         Stack2<T> s = (Stack2<T>)super.clone(); //Clone the stack.
         s.items =  (ArrayList<T>)items.clone(); //Clone the list.
         return s; // Return the clone
      } catch (CloneNotSupportedException e) {
         //This shouldn't happen because Stack is Cloneable.
         throw new InternalError();
      }
   }
}