/* Written by Jen Chen
   Updated on March the 4th, 2003
   Copyrighted by Jen Chen
*/
import java.util.*;
import java.io.*;

public class myStack extends Vector implements Cloneable, Collection, List, Serializable{
  private int CAPACITY=100;  
  private int size = -1;  //empty stack at the beginning.
  private Object[] obj = new Object[CAPACITY]; //create an array of object.

  public myStack(){}
  public myStack(int capacity){this.CAPACITY = capacity;}

  public int size(){ return size + 1;}  //return the number of elements on the stack.
  public void push(Object o){
    if(isFull())
      System.out.println("Stack is full, can not add more element!");
    else{
      ++size;
      obj[size] = o;  //remember to increment the size of the stack BEFORE
    }
  }     //ADDING an element to the stack. Otherwise, stack overflow will occur.

  public Object pop(){
    if(isEmpty())
      return ("Stack is empty!");
    else
      return obj[size--];
    }

  public void peek(){
    if(isEmpty())
      System.out.println("Stack is empty!");
    System.out.println(obj[size]);
  }

  public boolean isEmpty(){
    if( size < 0)
      return true;
    else
      return false;
  }

  public boolean isFull(){
    if(size == CAPACITY - 1)
      return true;
    else
      return false;
  }
}//end of class myStack{}