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.
1. every time n&1, until n==0.
2. n&(n-1) will remove last 1 digit in n, use this to count how many 1 in the number
public int hammingWeight(int n) {int count = 0;while(n!=0){n = (n-1) & n;count++;}return count;}