JAVA数据结构之循环队列的实现

1、循环队列CircleQueue类的实现代码如下所示：

public class CircleQueue {
	private Object[] array;
	private int capacity;//队列容量
	private int count;//队列中元素的个数
	private int front;
	private int rear;

	public CircleQueue(int capacity){
		this.capacity = capacity;
		array = new Object[capacity];
		count = 0;
		front = 0;
		rear = 0;
	}

	//入队
	public boolean append(Object data){
		boolean ret = (array != null) && (capacity > 0);

		if(ret){
			array[rear] = data;
			rear = (rear + 1) % capacity;

			count++;

			if(count > capacity){
				count = capacity;
			}
		}

		return ret;
	}

	//出队
	public Object retrieve(){
		Object data = null;

		if((array != null) && (capacity > 0) && (count > 0)){
			data = array[front];
			array[front] = null;
			front = (front + 1) % capacity;
			count--;
		}

		return data;
	}

	//获取队列中元素的个数
	public int getCount(){
		return count;
	}

	//获取队列的容量
	public int getCapacity(){
		return capacity;
	}

	//查看队头的数据，只查看，不删除。
	public Object getHead(){
		Object ret = null;

		if(array != null && capacity > 0 && count > 0){
			ret = array[front];
		}

		return ret;
	}

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

	//清空队列中的元素
	public void clear(){
		array = null;
		array = new Object[capacity];
		count = 0;
		front = 0;
		rear = 0;
	}

	public void destroy(){
		array = null;
		count = 0;
		front = 0;
		rear = 0;
	}
}

2、测试类Test的实现代码如下所示：

public class Test {

	public static void main(String[] args) {
		CircleQueue queue = new CircleQueue(5);
		queue.append("元素1");
		queue.append("元素2");
		queue.append("元素3");
		queue.append("元素4");
		queue.append("元素5");
		queue.append("元素6");
		queue.append("元素7");

		System.out.println("队列的容量："+queue.getCapacity());
		System.out.println("队列中元素的个数："+queue.getCount());
		System.out.println("队列是否为空？"+queue.isEmpty());
		System.out.println("队头元素："+queue.getHead());
		System.out.println("出队：");

		while(!queue.isEmpty()){
			System.out.print(queue.retrieve()+"  ");
		}

		queue.clear();
		System.out.println("\n\n队列的容量："+queue.getCapacity());
		System.out.println("队列中元素的个数："+queue.getCount());
		System.out.println("队列是否为空？"+queue.isEmpty());

		queue.destroy();
	}
}