java实现队列与循环队列

public class Queue {
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    public Queue(int maxSize) {
        this.maxSize = maxSize;
        arr = new int[maxSize];
        front = -1;
        rear = -1;
    }

    // 判断队列是否满
    public boolean isFull() {
        return rear == maxSize - 1;
    }

    // 判断队列是否空
    public boolean isEmpty() {
        return front == rear;
    }

    // 入队
    public void inQueue(int n) {
        if (isFull()) {
            throw new RuntimeException("队列已满");
        }
        arr[++rear] = n;
    }

    // 出队
    public int outQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空");
        }
        return arr[++front];
    }

    // 打印队列
    public void show() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空");
        } else {
            for (int i : arr) {
                System.out.print(i + " ");
            }
        }
    }
}

front: arr[front]为队列第一个元素,初始值front = 0
rear：rear指向最后一个元素的后一个位置，初始值rear = 0
  队列满：(rear + 1) % maxSize == front
  队列为空： rear == front
  队列有效数据的个数（rear + maxSize -front) % maxSize

public class LoopQueue {
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    public LoopQueue(int maxSize) {
        this.maxSize = maxSize;
        arr = new int[maxSize];
        rear = 0;
        front = 0;
    }

    // 判断队列是否满
    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }

    // 判断队列是否空
    public boolean isEmpty() {
        return rear == front;
    }

    // 入队
    public void inQueue(int n) {
        if (isFull()) {
            throw  new RuntimeException("队列已满");
        }
        arr[rear] = n;
        rear = (rear + 1) % maxSize;
    }

    // 出队
    public int outQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空");
        }
        int tmp = arr[front];
        front = (front + 1) % maxSize;
        return tmp;
    }

    // 获取队列元素个数
    public int getElementCount() {
        return (rear + maxSize -front) % maxSize;
    }

    // 打印队列元素
    public void show() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空");
        }
        for (int i = front; i < (front + getElementCount()); i++) {
            System.out.println(arr[i % maxSize]);
        }
    }
}