环形队列

  • 队列是一种先进先出的数据结构

代码思路

  • 用数组寄存队列的数据
  • front指向队首元素
  • rear指向队尾元素
  • num寄存以后曾经存在的元素个数，有了num，判断队列是否为空是否存满比拟不便
public class Demo2 {    public static void main(String[] args) {        ArrayQueue queue = new ArrayQueue(5);        queue.addNum(10001);        queue.addNum(10002);        queue.addNum(10003);        queue.addNum(10004);        queue.addNum(10005);        System.out.println(queue.getNum());        System.out.println(queue.getNum());        queue.addNum(1);        queue.addNum(2);        queue.addNum(3);        queue.showQueue();        System.out.println(queue.getNum());        System.out.println(queue.getNum());        System.out.println(queue.getNum());        System.out.println(queue.getNum());        System.out.println(queue.getNum());        System.out.println(queue.getNum());    }}class ArrayQueue {    //队列的大小    int maxSize;    //用数组来实现队列    int[] arr;    //指向队列首元素    int front;    //指向队列尾元素    int rear;    //以后队列的元素的个数    int num;    public ArrayQueue(int maxSize) {        this.maxSize = maxSize;        this.arr = new int[this.maxSize];        front = -1;        rear = -1;    }    public boolean isFull() {        return num == maxSize;    }    public boolean isEmpty() {        return num == 0;    }    public void addNum(int num) {        if (isFull()) {            System.out.println("队列已满，无奈在进行入队操作");            return;        }        //队尾标记后移，指向要放入的元素的地位        if (front == -1 && rear == -1) {            front = 0;            rear = 0;        } else {            rear = rear + 1;        }        if (rear == maxSize) {            rear = 0;        }        arr[rear] = num;        this.num++;    }    public int getNum() {        if (isEmpty()) {            throw new RuntimeException("队列为空，无奈出队");        }        //队首标记后移，指向队首元素        System.out.print("出队元素是：");        this.num--;        int res = arr[front];        front++;        if (front == maxSize) {            front = 0;        }        return res;    }    public void showQueue() {        if (isEmpty()) {            throw new RuntimeException("队列为空，无奈遍历");        }        System.out.println("遍历队列");        if (rear >= front) {            for (int start = front; start <= rear; start++) {                System.out.println(arr[start]);            }        } else {            for (int start = front; start <= maxSize - 1; start++) {                System.out.println(arr[start]);            }            for (int start = 0; start <= rear; start++) {                System.out.println(arr[start]);            }        }    }}