Java循环队列简单实现

public class Queue {

    private int MAX_CAPACITY;
    private int[] data;
    private int front;
    private int rear;
    private int nItems;

    public Queue(int capacity){
        if(capacity < 0)
            throw new IllegalArgumentException("Illegal capacity: " + capacity);
        MAX_CAPACITY = capacity;
        data = new int[MAX_CAPACITY];
        front = 0;
        rear = -1;
        nItems = 0;
    }

    public Queue(){
        this(10);
    }

    public void insert(int value){
        if(isFull())
            throw new FullQueueException("queue is full");
        if(rear == MAX_CAPACITY-1)  // 因为是数组实现,所以数组顶端应该是MAX_CAPACITY-1
            rear = -1;              // 为什么初始状态是-1,因为数组下标从0开始
        data[++rear] = value;
        nItems++;
    }

    public int remove(){
        if(isEmpty())
            throw new EmptyQueueException("queue is empty");
        int temp = data[front++];
        if(front == MAX_CAPACITY)
            front = 0;             // 数组下标从0开始,front=0可以直接取
        nItems--;                  // 多维护一个队列大小变量,可以让isFull()、isEmpty()函数变得很简洁
        return temp;
    }

    public int peek(){
        if(isEmpty())
            throw new EmptyQueueException("queue is empty");
        return data[front];
    }

    public boolean isFull(){
        return (nItems == MAX_CAPACITY);
    }

    public boolean isEmpty(){
        return (nItems == 0);
    }

    public int size(){
        return nItems;
    }

    public static void main(String[] args) {
        Random random = new Random();
        Queue queue = new Queue();
        int CAPACITY = 10;
        System.out.println("----入列-----");
        for(int i=0;i100));
        }
        System.out.println("元素数量:" + queue.size());
        System.out.println("----出列-----");
        for(int i=0;iout.println(queue.remove());
        }
    }
}

注意几点：
1、解决”假溢出”问题:循环队列
2、担心rear一直循环会覆盖原来的值？:在insert之前加入isFull()判断,如果队列满(front==rear),则不会继续插入
3、担心front一直循环会取不到值？:在remove之前加入isEmpty()判断,如果队列为空(front==rear),则不会继续取值
4、front和rear一直互相追着跑
5、ADT中多维护一个变量(标识当前队列中元素数量),会让isFull()、isEmpty()代码简洁很多
6、异常处理原理同堆栈