diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..485dee64
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.idea
diff --git a/.java-version b/.java-version
new file mode 100644
index 00000000..43ab1570
--- /dev/null
+++ b/.java-version
@@ -0,0 +1 @@
+corretto64-11.0.15
diff --git a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example1.java b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example1.java
index 384e5ec2..299ce07e 100644
--- a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example1.java
+++ b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example1.java
@@ -4,7 +4,7 @@
 
 public class Example1 {
 
-    public void example1() {
+    public static void example1() {
         
         Optional<String> lowername = Optional.of("hello world"); // may be empty as well
 
diff --git a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example2.java b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example2.java
index 764c0791..56e17d97 100644
--- a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example2.java
+++ b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example2.java
@@ -8,7 +8,7 @@ public class Example2 {
 
     private static final String NOT_FOUND = "NOT FOUND";
     
-    public void example2() {
+    public static void example2() {
 
         List<Book> books = Arrays.asList();
 
diff --git a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example3.java b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example3.java
index e81535a6..e037f623 100644
--- a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example3.java
+++ b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Example3.java
@@ -8,7 +8,7 @@ public class Example3 {
 
     private static final String NOT_FOUND = "NOT FOUND";
 
-    public void example3() {
+    public static void example3() {
         
         List<Book> books = Arrays.asList();
 
diff --git a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Main.java b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Main.java
index 21ca1c15..1eda636a 100644
--- a/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Main.java
+++ b/Chapter12/P245_OptionalMapAndFlatMap/src/modern/challenge/Main.java
@@ -5,6 +5,7 @@ public class Main {
     public static void main(String[] args) {                       
         
         // check Example1, Example2 and Example3 classes
+        Example2.example2();
     }
 
 }