一个泛型栈类(GenericStack)

public class GenericStack<E> {
  private java.util.ArrayList<E> list = new java.util.ArrayList<E> ();
  
  public int getSize() {
	  return list.size();
  }
  // get peek of the stack
  public E peek() {
	  return list.get(getSize() - 1);
  }
  // push an E element into stack
  public void push(E o) {
	  list.add(o);
  }
  
  // pop and get peek Element
  public E pop() {
	  E o = list.get(getSize()-1);
	  list.remove(getSize()-1);
	  return o;
  }
  
  public boolean isEmpty() {
	  return list.isEmpty();
  }
}