二进制中1的个数

public class Count1 {

//循环次数为num的位数
public static int count2(int num){

    int count = 0;

    int flag = 1;

    while (flag != 0){
        if((num & flag) != 0){
            count++;
        }

        flag = flag << 1;
    }
    return count;
}

public static int count1(int num){
    int count = 0;

    while (num != 0){
        num = num & num-1;
        count++;
    }

    return count;
}

public static void main(String[] args){
    System.out.println(Count1.count1(0));
}
}