Implement queue using stacks

Implement the following operations of a queue using stacks.
push(x) -- Push element x to the back of queue.
pop() -- Removes the element from in front of queue.
peek() -- Get the front element.
empty() -- Return whether the queue is empty.

• Time: O(n) Space: O(n)

class MyQueue {
    Stack<Integer> input = new Stack<>();
    Stack<Integer> output = new Stack<>();
    public void push(int x) {
        input.push(x);
    }
    public void pop() {
        peek();
        output.pop();
    }
    public int peek() {
        if (output.empty())
            while (!input.empty())
                output.push(input.pop());
        return output.peek();
    }
    public boolean empty() {
        return input.empty() && output.empty();
    }
}