盒子趣题

哈哈，再分享道有意思的题目，代码其实很简单，主要是想明白~
定义一个盒子类，有一个属性，三个方法：

public class Box{
    Boolean flag = false;
    public Box(){
    }

    public void open(){
        flag=true;
    }
    public void close(){
        flag=false;
    }
    public void reverse(){
        flag=!(flag);
    }
}

再定义个Test类：

public  class TestBox {
    public static void main(String[] args) {
        final int total =1000;
        Box[] b = new Box[total];
        for (int i =0;i<total;i++){
            b[i]=new Box();
        }
        //the first person
        for (int i =0;i<total;i++) {
            b[i].open();
        }

    //the second person
    for (int i = 1; i < total; i = i + 2) {
        b[i].close();
    }

    //the third person and the last
    for (int a = 3; a <= total; a++) {
        for (int i = a-1; i < total; i = i + a) {
            b[i].reverse();
        }

    }
    int count=0;
    for (int i =0;i<total;i++){
        if (b[i].flag==true){
            count++;
        }
    }
    System.out.println(count);
}

}