数据结构-队列(循环)-2015

循环队列，重点是队空 或 队满 的判断。

/**
 * 循环队列，重点是队空 或 队满 的判断
 */
public class QueueDemo {
	private static int maxSize = 5;
	private Object[] array;
	private int front;       //队头
	private int rear;        //队尾
    private int nItems = 0;  
    
    public QueueDemo(){
    	this(maxSize);
    }
    
    private QueueDemo(int size){
    	int front = 0;
    	int rear = 0;
    	
    	array = new Object[size];
    }
    
    public void insert(Object obj){
    	if(rear + 1 % maxSize == front){
    		System.out.println("队列满。");
    		return;
    	}
    	
    	/*if(rear + 1 == maxSize)
    		rear = 0;*/
    	
    	array[rear] = obj;
    	nItems++;
    	
    	if(this.isFull()){
    		throw new RuntimeException("队列满==========");
    	}
    	rear = (rear + 1) % maxSize;
    	
    }
    
    public Object remove(){
    	if( rear == front){
    		throw new RuntimeException("队列空==========");
    	}
    	
    	Object obj = array[front];
    	
    	front = (front + 1) % maxSize;
    	
    	nItems--;
    	return obj;
    }
    
    public Object peek(){
    	Object obj = array[front];
    	
    	return obj;
    }
    
    public boolean isFull(){
    	boolean flag = false;
    	if(nItems >= maxSize)
    		flag = true;
    	return flag;
    }
    
    public boolean isEmpty(){
    	boolean flag = false;
    	if(nItems == 0)
    		flag = true;
    	
    	return flag;
    }
    
    public int size(){
    	return nItems;
    }
    
    public void display(){
    	while(nItems > 0){
    		Object obj = this.remove();
    		System.out.println("-->" + obj);
    	}
    }
    public static void main(String[] args){
    	QueueDemo queue = new QueueDemo();
    	
		/*测试1 队列满
		queue.insert("a");
    	queue.insert("b");
    	queue.insert("c");
    	queue.insert("d");
    	queue.insert("e");
    	queue.insert("f");
    	*/
    	
    	/*测试2 队列空*/
    	queue.insert("a");
    	queue.insert("b");
    	queue.remove();
    	queue.remove();
    	queue.remove();
    	
//    	queue.display();
    	System.out.println(queue);
    	
    	System.out.println("end========");

    }
}