diff --git a/src/main/java/com/leetcode/easy/NumberOf1Bits191.java b/src/main/java/com/leetcode/easy/NumberOf1Bits191.java
new file mode 100644
index 0000000..83728d0
--- /dev/null
+++ b/src/main/java/com/leetcode/easy/NumberOf1Bits191.java
@@ -0,0 +1,19 @@
+// Tags: Bit Manipulation, Divide and Conquer
+package com.leetcode.easy;
+
+public class NumberOf1Bits191 {
+    /**
+     * Time complexity: O(1)
+     * Space complexity: O(1)
+     */
+    public int hammingWeight(int n) {
+        int res = 0;
+        while (n != 0) {
+            if (n % 2 == 1) {
+                res++;
+            }
+            n = n >> 1;
+        }
+        return res;
+    }
+}
diff --git a/src/test/java/com/leetcode/easy/NumberOf1Bits191Test.java b/src/test/java/com/leetcode/easy/NumberOf1Bits191Test.java
new file mode 100644
index 0000000..2a8e3ae
--- /dev/null
+++ b/src/test/java/com/leetcode/easy/NumberOf1Bits191Test.java
@@ -0,0 +1,39 @@
+package com.leetcode.easy;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class NumberOf1Bits191Test {
+    private NumberOf1Bits191 solution;
+
+    @BeforeEach
+    void setUp() {
+        solution = new NumberOf1Bits191();
+    }
+
+    @Test
+    void testHammingWeight_Example1() {
+        int n = 11; // Binary representation: 1011
+        int expected = 3;
+        int result = solution.hammingWeight(n);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testHammingWeight_Example2() {
+        int n = 128; // Binary representation: 10000000
+        int expected = 1;
+        int result = solution.hammingWeight(n);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testHammingWeight_Example3() {
+        int n = 2147483645; // Binary representation: 1111111111111111111111111111101
+        int expected = 30;
+        int result = solution.hammingWeight(n);
+        assertEquals(expected, result);
+    }
+}