diff --git a/number-of-1-bits/JeonJe.java b/number-of-1-bits/JeonJe.java
new file mode 100644
index 0000000000..6199171708
--- /dev/null
+++ b/number-of-1-bits/JeonJe.java
@@ -0,0 +1,17 @@
+import java.util.*;
+
+// TC: O(1)
+// SC: O(1)
+class Solution {
+    public int hammingWeight(int n) {
+        int answer = 0;
+
+        while (n != 0) {
+            if ((n & 1) == 1) {
+                answer++;
+            }
+            n = n >>> 1;
+        }
+        return answer;
+    }
+}
diff --git a/valid-palindrome/JeonJe.java b/valid-palindrome/JeonJe.java
new file mode 100644
index 0000000000..7892c22f6d
--- /dev/null
+++ b/valid-palindrome/JeonJe.java
@@ -0,0 +1,23 @@
+import java.util.*;
+
+// TC: O(n)
+// SC: O(n)
+class Solution {
+    public boolean isPalindrome(String s) {
+        StringBuilder sb = new StringBuilder();
+
+        for (char c : s.toCharArray()) {
+            if (Character.isLetterOrDigit(c)) {
+                sb.append(Character.toLowerCase(c));
+            }
+        }
+
+        for (int i = 0; i < sb.length() / 2; i++) {
+            if (sb.charAt(i) != sb.charAt(sb.length() - 1 - i)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+}