public class arraystack implements stack{
	public static final int CAPACITY=100;
	private int capacity;
	private Object s[];
	private int top=-1;
	public arraystack(){
		this (CAPACITY);
	}
	
	public arraystack(int cap){
		capacity=cap;
		s=new Object[capacity];
	}
	
	public int size(){
		return (top+1);
		}
		
		public boolean isempty()
		{return(top<0);
			}
			
			public void push(Object e){
				s[++top]=e;
				}
				
				public Object top(){
					return s[top];
					}
					
					public Object pop(){
						Object element ;
						element = s[top];
						s[top--]=null;
						return element;
						}
						
					}