add solution for number-of-1-bits

Author: Ujoonnee

number-of-1-bits/Ujoonnee.java

@@ -0,0 +1,19 @@
+class Solution {
+    public int hammingWeight(int n) {
+        int answer = 0;
+        while (n > 0) {
+            answer += n & 1;
+            n >>= 1;
+        }
+
+        return answer;
+    }
+}
+
+/*
+class Solution {
+    public int hammingWeight(int n) {
+        return Integer.toBinaryString(n).replace("0", "").length();
+    }
+}
+*/