用两个栈来实现一个队列

import java.util.Stack;

public class  {
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();

    public void push(int node) {
        stack1.push(node);
    }

    public int pop() {
        while(!stack1.isEmpty()){
            stack2.push(stack1.pop());
        }
        int first = stack2.pop();
        while(!stack2.isEmpty()){
            stack1.push(stack2.pop());
        }
        return first;
    }
}