public class StatckQueue {
private Stack<Integer> stackA=new Stack<Integer>();
private Stack<Integer> stackB=new Stack<Integer>();
public void enQueue(int element){
stackA.push(element);
}
public Integer deQueue(){
if(stackB.isEmpty()){
if(stackA.isEmpty()){
return null;
}
transfer();
}
return stackB.pop();
}
private void transfer(){
while(!stackA.isEmpty()){
stackB.push(stackA.pop());
}
}
public static void main(String[] args) throws Exception{
StatckQueue stackQueue= new StatckQueue();
stackQueue.enQueue(1);
stackQueue.enQueue(2);
stackQueue.enQueue(3);
System.out.println(stackQueue.deQueue());
System.out.println(stackQueue.deQueue());
stackQueue.enQueue(4);
System.out.println(stackQueue.deQueue());
System.out.println(stackQueue.deQueue());
}
}