java循环队列实现

要实现循环队列，我们可以使用数组作为底层数据结构，并使用两个指针来表示队列的头部和尾部。具体实现如下：

public class CircularQueue {
    private int[] queue;
    private int front;
    private int rear;
    private int size;
    
    public CircularQueue(int capacity) {
        queue = new int[capacity];
        front = 0;
        rear = -1;
        size = 0;
    }
    
    public boolean isEmpty() {
        return size == 0;
    }
    
    public boolean isFull() {
        return size == queue.length;
    }
    
    public void enqueue(int item) {
        if (isFull()) {
            throw new IllegalStateException("Queue is full");
        }
        rear = (rear + 1) % queue.length;
        queue[rear] = item;
        size++;
    }
    
    public int dequeue() {
        if (isEmpty()) {
            throw new IllegalStateException("Queue is empty");
        }
        int item = queue[front];
        front = (front + 1) % queue.length;
        size--;
        return item;
    }
    
    public int peek() {
        if (isEmpty()) {
            throw new IllegalStateException("Queue is empty");
        }
        return queue[front];
    }
    
    public int size() {
        return size;
    }
}

使用示例：

CircularQueue queue = new CircularQueue(5);
queue.enqueue(1);
queue.enqueue(2);
queue.enqueue(3);

System.out.println(queue.dequeue()); // 输出：1
System.out.println(queue.peek()); // 输出：2
System.out.println(queue.size()); // 输出：2