diff --git a/longest-palindromic-substring/kimjunyoung90.java b/longest-palindromic-substring/kimjunyoung90.java
new file mode 100644
index 0000000000..9288714490
--- /dev/null
+++ b/longest-palindromic-substring/kimjunyoung90.java
@@ -0,0 +1,24 @@
+/**
+ * 시간복잡도 : O(n)
+ * 공간복잡도 : O(n)
+ */
+public class kimjunyoung90 {
+    public boolean isPalindrome(String s) {
+        //1. 대문자를 소문자로 변환
+        s = s.toLowerCase();
+
+        //2. 영어 숫자 외 문자 제거
+        s = s.replaceAll("[^a-z0-9]", "");
+
+        //3. 앞에서 읽나 뒤에서 읽나 동일한지 확인(pointer 사용)
+        int left = 0, right = s.length() - 1;
+        while(left < right) {
+            char leftChar = s.charAt(left);
+            char rightChar = s.charAt(right);
+            if(leftChar != rightChar) return false;
+            left++;
+            right--;
+        }
+        return true;
+    }
+}
diff --git a/maximum-subarray/kimjunyoung90.java b/maximum-subarray/kimjunyoung90.java
new file mode 100644
index 0000000000..cb337628f9
--- /dev/null
+++ b/maximum-subarray/kimjunyoung90.java
@@ -0,0 +1,15 @@
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        int max = Integer.MIN_VALUE;
+        for(int i = 0; i < nums.length; i++) {
+            for (int j = i; j < nums.length; j++) {
+                int sum = 0;
+                for(int k = i; k <= j; k++) {
+                    sum+= nums[k];
+                }
+                max = Math.max(max, sum);
+            }
+        }
+        return max;
+    }
+}