https://leetcode.com/problems/number-of-1-bits/description/

HammingWeightCalculator.java

class HammingWeightCalculator {
    public static void main(String[] args) {
        System.out.println(new HammingWeightCalculator().hammingWeight(11));
        System.out.println(new HammingWeightCalculator().hammingWeight(128));
        System.out.println(new HammingWeightCalculator().hammingWeight(2147483645));
    }

    public int hammingWeight(int n) {
        String value = Integer.toBinaryString(n);
        int returnValue = 0;
        for (Character c: value.toCharArray()){
            if(c=='1')
                returnValue++;
        }
        return returnValue;
    }
}