Stack.java

package basic;

public class Stack {

	private ArrayList elementData = new ArrayList();
	
	private int size = 0;
	
	public void push(Object o){
		elementData.add(o);
		size++;
	}
	
	public Object pop(){
		return elementData.remove(size-1);
	}
	
	public Object peek(){
		return elementData.get(size-1);
	}
	
	public boolean isEmpty(){
		return size == 0;
	}
	
	public int size(){
		return size;
	}
}