diff --git a/src/leetcode/num3/java/Main.java b/src/leetcode/num3/java/Main.java
new file mode 100644
index 0000000..fc8e4b4
--- /dev/null
+++ b/src/leetcode/num3/java/Main.java
@@ -0,0 +1,21 @@
+package leetcode.num3.java;
+
+public class Main {
+
+    static void lengthOfLongestSubstring(String s) {
+        char[] charArray = s.toCharArray();
+        int[] locArray = new int[charArray.length];
+        for(int i = 0; i < locArray.length; i++) {
+            locArray[i] = i + 1;
+        }
+        for(int i = 0; i < charArray.length; i++) {
+            for(int j = i - 1; j >= 0; j--) {
+                if(charArray[i] == charArray[j]) {
+                    locArray[i] = i - j;
+                    break;
+                }
+            }
+        }
+
+    }
+}