queue1.java

//implementing queues using stacks
import java.util.*;
public class Queueviastack
{
 static class Queue
 {
 static Stack<Integer> s1 = new Stack<Integer>();
 static Stack<Integer> s2 = new Stack<Integer>();
 
 static void enQueue(int x)
 {
 while(!s1.isEmpty())
 {
 s2.push(s1.pop());
 }
 s1.push(x);
 while(!s2.isEmpty())
 {
 s1.push(s2.pop());
 }
 }
 static int deQueue()
 {
 if(s1.isEmpty())
 {
 System.out.println("Queue is Empty");
 System.exit(0);
 }
 int x=s1.peek();
 s1.pop();
 return x;
 }
 }
 public static void main(String args[])
 {
 Queue q = new Queue();
 q.enQueue(3);
 q.enQueue(6);
 q.enQueue(9);
 
 System.out.println(q.deQueue());
 System.out.println(q.deQueue());
 System.out.println(q.deQueue());
 }
 
}