用两个栈实现队列

import java.util.Stack;

public class Solution {
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();
    
     public void push(int node) {
        stack1.push(node);
    }
     
    public int pop() {
        if(stack1.empty()&&stack2.empty()){
            throw new RuntimeException("Queue is empty");
        }
        if(stack2.empty()){
            while(!stack1.empty()){
                stack2.push(stack1.pop());//把stack1的值弹出后再压入stack2中
            }
        }
        return stack2.pop();//弹出
    }
}