package top.baikunlong.queue;import java.util.Scanner;/*** @author baikunlong* @date 2020/10/7 11:53*/
public class ArrayQueue {private int maxSize;//最大容量，实际存储只有maxSize-1，有一个空间为预留空间。private int front;//队头private int rear;//队尾private int[] arr;public ArrayQueue(int maxSize) {this.maxSize = maxSize;arr = new int[maxSize];}public boolean isFull() {//这里要预留一个空间，也就是有一个空间永远是利用不了的，不然rear==front了，区别不了是空队列还是满队列。。。return (rear + 1) % maxSize == front;}public boolean isEmpty() {return rear == front;}/*** 入队** @param n*/public void add(int n) {if (isFull()) {System.out.println("队列已满");} else {arr[rear] = n;rear = (rear + 1) % maxSize;}}/*** 出队，会移除数据** @return*/public int poll() {if (isEmpty()) {throw new RuntimeException("队列为空");} else {int n = arr[front];front = (front + 1) % maxSize;return n;}}/*** 打印队列*/public void show() {//从front开始遍历，遍历到front+sizefor (int i = front; i < front+size(); i++) {System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);}}/*** 当前队列有效个数** @return*/public int size() {return (rear + maxSize - front) % maxSize;}public static void main(String[] args) {ArrayQueue queue = new ArrayQueue(4);Scanner scanner = new Scanner(System.in);while (true) {System.out.println("a(add): 添加数据到队列");System.out.println("p(poll): 从队列取出数据");System.out.println("s(show): 显示队列");System.out.println("e(exit): 退出程序");String s = scanner.nextLine();switch (s) {case "a":queue.add(scanner.nextInt());break;case "p":try {System.out.println("出队得到："+queue.poll());} catch (Exception e) {System.out.println(e.getMessage());}break;case "s":queue.show();break;case "e":System.exit(0);break;}}}
}