Leetcode: 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.
Notes:
You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).

Lintcode: http://www.cnblogs.com/EdwardLiu/p/4278333.html

class MyQueue {
    // Push element x to the back of queue.
    LinkedList<Integer> stack1;
    LinkedList<Integer> stack2;
    
    public MyQueue() {
        this.stack1 = new LinkedList<Integer>();
        this.stack2 = new LinkedList<Integer>();
    }
    
    public void push(int x) {
        stack1.push(x);
    }

    // Removes the element from in front of queue.
    public void pop() {
        if (!stack2.isEmpty()) {
            stack2.pop();
            return;
        }
        while (!stack1.isEmpty()) {
            stack2.push(stack1.pop());
        }
        if (!stack2.isEmpty()) stack2.pop();
    }

    // Get the front element.
    public int peek() {
        if (!stack2.isEmpty()) return stack2.peek();
        else while (!stack1.isEmpty()) {
            stack2.push(stack1.pop());
        }
        return stack2.peek();
    }

    // Return whether the queue is empty.
    public boolean empty() {
        return (stack1.isEmpty() && stack2.isEmpty());
    }
}