Implement Queue using Stacks Java

PROGRAM TO IMPLEMENT QUEUE USING STACKS

import java.util.*;

  

class GFG 

{ 

static class Queue 

{ 

    static Stack<Integer> s1 = new Stack<Integer>(); 

    static Stack<Integer> s2 = new Stack<Integer>(); 

  

    static void enQueue(int x) 

    { 

        // Move all elements from s1 to s2 

        while (!s1.isEmpty())

        { 

            s2.push(s1.pop()); 

            //s1.pop(); 

        } 

  

        // Push item into s1 

        s1.push(x); 

  

        // Push everything back to s1 

        while (!s2.isEmpty()) 

        { 

            s1.push(s2.pop()); 

            //s2.pop(); 

        } 

    } 

  

    // Dequeue an item from the queue 

    static int deQueue() 

    { 

        // if first stack is empty 

        if (s1.isEmpty()) 

        { 

            System.out.println("Q is Empty"); 

            System.exit(0); 

        } 

  

        // Return top of s1 

        int x = s1.peek(); 

        s1.pop(); 

        return x; 

    } 

}; 

  

// Driver code 

public static void main(String[] args) 

{ 

    Queue q = new Queue(); 

    q.enQueue(1); 

    q.enQueue(2); 

    q.enQueue(3); 

  

    System.out.println(q.deQueue()); 

    System.out.println(q.deQueue());

    System.out.println(q.deQueue());

} 

} 




OUTPUT:

1
2
3

CREDITS: https://www.geeksforgeeks.org/queue-using-stacks/