import java.util.*; 
//
// First In First Out
// Stack 
//
//
public class FIFO{ 
	Vector list;
	int length=0;
	FIFO(){
		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);
		length=list.size();
	}

	// Get the first available member and remove it
	public String pop(){
		String retval=null;
		if(!list.isEmpty()){
			retval=(String)list.firstElement();
			list.removeElementAt(0);
		}
		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.firstElement();
		}
		return retval;
	}


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

}