232. Implement Queue using Stacks Java Solutions

 1 class MyQueue {
 2     Stack<Integer> s1 = new Stack<Integer>();
 3     Stack<Integer> s2 = new Stack<Integer>();
 4     // Push element x to the back of queue.
 5     public void push(int x) {
 6         s1.push(x);
 7     }
 8 
 9     // Removes the element from in front of queue.
10     public void pop() {
11         if(!s2.isEmpty()) s2.pop();
12         else{
13             while(!s1.isEmpty()) s2.push(s1.pop());
14             s2.pop();
15         }
16     }
17 
18     // Get the front element.
19     public int peek() {
20         if(!s2.isEmpty()) return s2.peek();
21         else{
22             while(!s1.isEmpty()) s2.push(s1.pop());
23             return s2.peek();
24         }
25     }
26 
27     // Return whether the queue is empty.
28     public boolean empty() {
29         return s1.isEmpty() && s2.isEmpty();
30     }
31 }