problems(java): add “191. Number of 1 Bits”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/java/number-of-1-bits.java

@@ -0,0 +1,13 @@
+public class Solution {
+    public int hammingWeight(int n) {
+        int bits = 0;
+
+        for (int i = 0; i < 32; ++i) {
+            if ((n & (1 << i)) != 0) {
+                ++bits;
+            }
+        }
+
+        return bits;
+    }
+}