CircleQueue.java

package com.coding.basic.queue;

import java.util.NoSuchElementException;

/**
 * 用数组实现循环队列
 * @author kai
 *
 * @param <E>
 */
public class CircleQueue <E> {
	
	private final static int DEFAULT_SIZE = 10;
	
	//用数组来保存循环队列的元素
	private Object[] elementData = new Object[DEFAULT_SIZE] ;
	
	//队头
	private int front = 0;  
	//队尾  
	private int rear = 0;
	
	public boolean isEmpty() {
		return front == rear;
        
    }

    public int size() {
        return (rear - front + DEFAULT_SIZE) % DEFAULT_SIZE;
    }

    public void enQueue(E data) {
        if((rear+1) % DEFAULT_SIZE == front){
        	throw new IndexOutOfBoundsException("Queue overflow");
        }
        rear = (rear+1) % DEFAULT_SIZE;
        elementData[rear] = data;
    }

    public E deQueue() {
    	if(isEmpty()){
    		throw new NoSuchElementException("Queue underflow"); 
    	}
    	
    	Object item = elementData[front];
    	front = (front + 1) % DEFAULT_SIZE;
        return (E) item;
    }
}