代码面试题：Count ones in binary

Count the number of 1’s in the binary expression of a given integer

Example: 

input: 90

output: 4

用位操作。

    public int countOnes(int x) {
    	int count = 0;
    	while (x != 0) {
    		x &= x - 1;
    		count++;
    	}
    	return count;
    }