public class MyStack { private java.util.ArrayList list = new java.util.ArrayList(); public boolean isEmpty() { return list.isEmpty(); } public int getSize() { return list.size(); } public Object peek() { return list.get(getSize() - 1); } public Object pop() { Object o = list.get(getSize() - 1); list.remove(getSize() - 1); return o; } public void push(Object o) { list.add(o); } /** Override the toString in the Object class */ public String toString() { return "stack: " + list.toString(); } }