package TestCollection;
public class Stack {
private ArrayList elementData = new ArrayList();
public void push(Object o){
elementData.add(o);
}
public Object pop(){
return elementData.get(elementData.size()-1) ;
}
public Object peek(){
elementData.remove(elementData.size()-1);
return elementData.get(elementData.size()-1);
}
public boolean isEmpty(){
if(elementData.size()!=0){
return false;}
return true;
}
public int size(){
return elementData.size();
}
public static void main(String[] args) {
Stack s=new Stack();
s.push("111");
s.push("211");
s.push("311");
System.out.println(s.size());//3
System.out.println(s.pop());
System.out.println(s.size());
System.out.println(s.peek());
System.out.println(s.size());
}}