java中的队列

java中的队列

常见的数据结构：https://blog.csdn.net/weixin_43304253/article/details/119764275

• 先进先出
  入队enqueue()，放一个数据到队列尾部；出队：dequeue()；从队列头部取出一个元素
  
  代码实现

package com.zheng.demo5;

public class MyQueue {
    public static void main(String[] args) {
        ArrayQueue queue = new ArrayQueue(6);
        queue.enqueue(1);
        queue.enqueue(2);
        queue.enqueue(3);
        queue.enqueue(4);
        System.out.println("遍历队列");
        queue.list();
        System.out.println("出队列两个数据：");

        System.out.println(queue.dequeue());
        System.out.println(queue.dequeue());

        System.out.println("出队列后");
        queue.list();

    }

}

class ArrayQueue {
    private int first;//队列头
    private int last;//队列尾
    private int sizeMax;//队列大小
    private int[] queue;//队列

    //构造函数初始化

    public ArrayQueue(int sizeMax) {
        this.sizeMax = sizeMax;
        queue = new int[this.sizeMax];
        first = this.sizeMax - 1;//将队列头和尾初始值为队列的最前端
        last = this.sizeMax - 1;

    }

    //判断队列是否满
    public boolean isFull() {
        return last == -1;//代表插入的数据满
    }

    //判断是否为空
    public boolean isEmpty() {
        return first == last;//当队列头和队列尾相同的情况下
    }

    //入队列
    public void enqueue(int data) {
        //判断队列是否满
        if (isFull()) {
            throw new RuntimeException("队列满");
        }

        queue[last] = data;
        last--;
    }

    //出队列
    public int dequeue() {
        //判断队列是否为空
        if (isEmpty()) {
            throw new RuntimeException("队列为空");
        }

        int val = queue[first];
        first--;
        return val;

    }

    //遍历
    public void list() {
        //判断队列是否为空
        if (isEmpty()) {
            throw new RuntimeException("队列为空");
        }
        for (int i = first; i > last; i--) {
            System.out.printf("queue[%d]=%d\n", i, queue[i]);

        }

    }


}