diff --git a/.gitignore b/.gitignore
index a1c2a23..4cad7a3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,3 +21,7 @@
 
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
+
+out/
+LeetcodeSolutionJava.iml
+.idea
\ No newline at end of file
diff --git a/src/AddTwoNumber.java b/src/AddTwoNumber.java
new file mode 100644
index 0000000..8f4a13d
--- /dev/null
+++ b/src/AddTwoNumber.java
@@ -0,0 +1,58 @@
+/*
+You are given two non-empty linked lists representing two non-negative integers.
+The digits are stored in reverse order and each of their nodes contain a single digit.
+Add the two numbers and return it as a linked list.
+You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+Example:
+Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
+Output: 7 -> 0 -> 8
+Explanation: 342 + 465 = 807.
+ */
+
+class Solution {
+
+    // Definition for singly-linked list
+    // static class
+    public static class ListNode {
+        int val;
+        ListNode next;
+
+        ListNode(int x) {
+            this.val = x;
+            this.next = null;
+        }
+    }
+
+    public ListNode addTwoNumber(ListNode l1, ListNode l2) {
+        if (l1 == null) {
+            return l2;
+        }
+
+        if (l2 == null) {
+            return l1;
+        }
+
+        ListNode newNode = new ListNode(0);
+        ListNode p = newNode;
+        int val;
+        int carry = 0;
+
+        while (l1 != null || l2 != null) {
+            int xVal = (l1 != null) ? l1.val : 0;
+            int yVal = (l2 != null) ? l2.val : 0;
+
+            val = (xVal + yVal + carry) % 10;
+            carry = (xVal + yVal + carry) / 10;
+            p.next = new ListNode(val);
+            p = p.next;
+            if (l1 != null) l1 = l1.next;
+            if (l2 != null) l2 = l2.next;
+        }
+
+        if (carry > 0) {
+            p.next = new ListNode(carry);
+        }
+
+        return newNode.next;
+    }
+}
diff --git a/src/HelloWorld.java b/src/HelloWorld.java
new file mode 100644
index 0000000..74f62ba
--- /dev/null
+++ b/src/HelloWorld.java
@@ -0,0 +1,5 @@
+public class HelloWorld {
+    public static void main(String[] args) {
+        System.out.println("Hello world");
+    }
+}