剑指offer09-两个栈实现队列

import java.util.Stack;
class CQueue {
　　　　 //要注意每一块写什么，构造函数初始化两个栈为linkedlist
        Deque<Integer> stack1;
        Deque<Integer> stack2;
        public CQueue() {
            stack1=new LinkedList();
            stack2=new LinkedList();
        }
        //插入直接在第一个插入

        public void appendTail(int value) {
            stack1.push(value);
  
        }
        //提取栈首位元素，stack1所有元素倒叙输出，输入到stack2，stack2再输出就是正序了
        public int deleteHead() {
            if(stack2.isEmpty()){
                while(!stack1.isEmpty()){
                    stack2.push(stack1.pop());
                }
            }
            if(stack2.isEmpty()){
                return -1;
            }else{
                return stack2.pop();
            }
            
            
        }
    }


/**
 * Your CQueue object will be instantiated and called as such:
 * CQueue obj = new CQueue();
 * obj.appendTail(value);
 * int param_2 = obj.deleteHead();
 */