二进制中1的个数

public class SumOfOne {
	//一个数n和n-1相与会去掉n的二进制表示中最低位的1
	public int sumOne(int num){
		int sum = 0;
		while(num != 0){
			sum += 1;
			num = num & (num - 1);
		}
		return sum;
	}
	public static void main(String[] args) {
		SumOfOne s = new SumOfOne();
		System.out.println(7);
	}
}