diff --git a/solution/0000-0099/0001.Two Sum/Solution.class b/solution/0000-0099/0001.Two Sum/Solution.class
new file mode 100644
index 0000000000000..ad7b8ec188295
Binary files /dev/null and b/solution/0000-0099/0001.Two Sum/Solution.class differ
diff --git a/solution/0000-0099/0001.Two Sum/Solution.java b/solution/0000-0099/0001.Two Sum/Solution.java
index 8399b8e0af458..26b87393728a0 100644
--- a/solution/0000-0099/0001.Two Sum/Solution.java	
+++ b/solution/0000-0099/0001.Two Sum/Solution.java	
@@ -1,3 +1,8 @@
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+
 class Solution {
     public int[] twoSum(int[] nums, int target) {
         Map<Integer, Integer> d = new HashMap<>();
@@ -10,4 +15,13 @@ public int[] twoSum(int[] nums, int target) {
             d.put(x, i);
         }
     }
+
+    public static void main(String[] args){
+        Solution s  = new Solution();
+        int[] nums = {2, 7, 11, 15};
+        int target = 9;
+        int[] result = s.twoSum(nums, target);
+        System.out.println("Result: "+ Arrays.toString(result));
+    }
+    
 }
diff --git a/solution/0000-0099/0001.Two Sum/java01.java b/solution/0000-0099/0001.Two Sum/java01.java
new file mode 100644
index 0000000000000..5f09914fb39fd
--- /dev/null
+++ b/solution/0000-0099/0001.Two Sum/java01.java	
@@ -0,0 +1,29 @@
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+
+
+public class java01 {
+    public int[] Sum(int[] nums, int target){
+        Map<Integer, Integer> d = new HashMap<>();
+                for (int i = 0;; ++i) {
+            int x = nums[i];
+            int y = target - x;
+            if (d.containsKey(y)) {
+                return new int[] {d.get(y), i};
+            }
+            d.put(x, i);
+        }
+    }
+    
+
+    public static void main(String[] args){
+        java01 s  = new java01();
+        int[] nums = {2, 7, 11, 15};
+        int target = 9;
+        int[] result = s.Sum(nums, target);
+        System.out.println("Result: "+ Arrays.toString(result));
+    }
+    
+}
diff --git a/solution/0000-0099/0002.Add Two Numbers/Solution.py b/solution/0000-0099/0002.Add Two Numbers/Solution.py
index efcb2b0b07f3e..f317322c24dc0 100644
--- a/solution/0000-0099/0002.Add Two Numbers/Solution.py	
+++ b/solution/0000-0099/0002.Add Two Numbers/Solution.py	
@@ -1,8 +1,11 @@
 # Definition for singly-linked list.
-# class ListNode:
-#     def __init__(self, val=0, next=None):
-#         self.val = val
-#         self.next = next
+from typing import Optional
+
+
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
 class Solution:
     def addTwoNumbers(
         self, l1: Optional[ListNode], l2: Optional[ListNode]