//stack2有元素就pop，没有元素就将stack1中所有元素倒进来再pop
     public static void push(int node) {
          stack1.push(node);
     }
     public static int pop() {
         if(stack1.isEmpty()&&stack2.isEmpty()){
             throw new RuntimeException("Queue is empty!");
         }
         if(stack2.isEmpty()){
             while (!stack1.isEmpty()){
                 stack2.push(stack1.pop());
             }
         }
         return stack2.pop();
     }

 //每次psuh是时先将stack2清空放入stck1(保证选入的一定在栈底)，stack2始终是用来删除的
     //在pop前，先将stack1中中的数据清空放入stack2（保存后入的在栈底），stack1始终用于push
     public static void push01(int node) {
         while(!stack2.isEmpty()){
             stack1.push(stack2.pop());
         }
         stack1.push(node);
     }

     public static int pop01() {
         while (!stack1.isEmpty()){
             stack2.push(stack1.pop());
         }
         return stack2.pop();
     }

 public static void main(String[] args) {
         String[] order={"PUSH_1","PUSH_2","PUSH_3","POP","POP","PUSH_4","POP","PUSH_5","POP","POP"};
         for(int i=0;i<order.length;i++){
             String s = order[i].toString();
             String[] strings = s.split("_");
             if(strings[0].equals("PUSH")){
                 int parseInt = Integer.parseInt(strings[1]);
                 push(parseInt);
             }
             if(strings[0].equals("POP")){
                 int pop = pop();
                 System.out.print(pop+" ");
             }
         }
     }
 输出：1 2 3 4 5