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.

解题思路：

本题用java来实现无符号int，所以我们不能使用取模和除法，应该使用位与和无符号右移来实现。

代码如下：

public class Solution {

    // you need to treat n as an unsigned value

    public int hammingWeight(int n) {

        int count = 0;

        while(n != 0){

        	count += (n & 1);

        	n = n >>> 1;

        }

        return count;

    }

}