java实现环形队列

/**
 * 队列：先进先出
 * 数组实现
 * first in first out
 * FIFO
 */
public class MyQueue {

    private Object[] arr = new Object[5];

    private int start = 0;

    private int end = 0;
	//插入元素
    public boolean offer(Object obj){
        if((end+1)%arr.length == start){
            return false;
        }
        arr[end] = obj;
        end++;
        end = end%arr.length;
        return true;
    }
	//查看队头元素
    public Object peek(){
        return arr[start];
    }
	//弹出元素
    public Object poll(){
        if(start == end){
            throw new NullPointerException();
        }
        Object temp = arr[start];
        start++;
        start = start%arr.length;
        return temp;
    }
	//获取队列内容长度
    public int size(){
        return (end+arr.length-start)%arr.length;
    }
}