题目描述：
Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).
For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.
本题依然属于一道位运算的题目，输入一个无符号的整数，判断出1的个数。
思路：
对于整数n,从n开始对n和n-1做与运算然后赋值给n。即，n=n&n-1。直到n等于n为止。能做多少次运算就说明有多少个1。
实现代码：
public class Solution {
public int HammingWeight(uint n) {
int count;
for (count=0; n > 0 ; count++){
n &= n-1;
}
return count;
}
}