QueueBy2Stacks.java

import java.util.Stack;

public class QueueBy2Stacks {
    static class Queue{
        static Stack<Integer> s1 = new Stack<>();
        static Stack<Integer> s2 = new Stack<>();
     
        public static boolean isEmpty(){
            return s1.isEmpty();
        }
        
        public static void add(int data){
            while (!s1.isEmpty()) {
                s2.push(s1.pop());
            }
            s1.push(data);
            while (!s2.isEmpty()) {
                s1.push(s2.pop());
            }
        }

        public static int remove(){
            return s1.pop();
        }

        public static int peek(){
            return s1.peek();
        }
    }

    @SuppressWarnings("static-access")
    public static void main(String[] args) {
        Queue q = new Queue();
        q.add(1);
        q.add(2);
        q.add(3);
        q.add(4);
        q.add(5);
        while (!q.isEmpty()) {
            System.out.println(q.peek());
            q.remove();
        }
    }
}