Leetcode Implement stack using queues

Implement the following operations of a stack using queues.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
empty() -- Return whether the stack is empty.

Notes:

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

也可以用2个queue。
2种思路：
Method 1 (By making push operation costly)
Method 2 (By making pop operation costly)，这里用的method2

class MyStack {

List<Integer> queue;
MyStack()
{
queue=new LinkedList<Integer>();
}

// Push element x onto stack.
public void push(int x) {
queue.add(x);
}

// Removes the element on top of the stack.
public void pop() {
if(queue.isEmpty())return;
int n=queue.size();
for(int i=0;i<n-1;i++)
{
queue.add(queue.remove(0));
}
queue.remove(0);
}

// Get the top element.
public int top() {
if(queue.isEmpty())return Integer.MAX_VALUE;
int n=queue.size();
for(int i=0;i<n-1;i++)
{
queue.add(queue.remove(0));
}
int r=queue.remove(0);
queue.add(r);
return r;
}

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