Number of 1 Bits

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.

一个数减1，它里面的是1的bit就会减少1个。

public int hammingWeight(int n) {int result=0;while(n!=0){result++;n&=(n-1);}return result;}