import java.util.*; 
//
// First In First Out
// Stack 
//
//
public class LIFO{ 
	Vector list;
	int l=0;
	LIFO(){
		list=new Vector();
	}
	// Put on stack  -- add below on the stack .. the first on the stack goes first off the stack
	public void push(String S){
		list.addElement((String)S);
		l++;
//		length=list.size();
	}

	// Get the first available member and remove it
	public String pop(){
		String retval=null;
		if(!list.isEmpty()){
			retval=(String)list.lastElement();
			list.removeElementAt(l);
		}
		l--;
//		length=list.size();
		return retval;
	}

	//Investigate the first available member without removing it!
	public String next(){
		String retval=null;
		if(!list.isEmpty()){
			retval=(String)list.lastElement();
		}
		return retval;
	}


	public boolean isEmpty(){
		return list.isEmpty();
	}
	public void clear(){
		list.clear();
		l=0;
//		while(!list.isEmpty()){
//			list.removeElementAt(0);
//		}
	}

}