Fix java READMES JDK

Author: en-sciappesoni

lessons/day_02/java/README.md

@@ -6,7 +6,7 @@ Read the instructions on the [Day 2 exercise](../day_02.md#exercise) definition
 
 ### Requirements
 
-Java 1.8 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+Java 17 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
 
 ### Keep in mind
 

lessons/day_03/java/README.md

@@ -1,12 +1,14 @@
 # [A walk in GraphQL](../../../README.md)
 
-## Day 2 exercise - Java
+## Day 3 exercise - Java
 
-Read the instructions on the [Day 2 exercise](../day_02.md#exercise) definition
+Read the instructions on the [Day 3 exercise](../day_03.md#exercise) definition
+
+HINT: Take a look at the commented out PersonService and SkillService methods!!
 
 ### Requirements
 
-Java 1.8 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+Java 17 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
 
 ### Keep in mind
 
@@ -28,3 +30,5 @@ See [Testing GraphQL queries](../../../setup/java.md#testing-graphql-queries)
 ### Database
 
 See [Inspect the Database](../../../setup/java.md#inspect-the-database)
+
+

lessons/day_04/java/README.md

@@ -1,12 +1,14 @@
 # [A walk in GraphQL](../../../README.md)
 
-## Day 2 exercise - Java
+## Day 4 exercise - Java
 
-Read the instructions on the [Day 2 exercise](../day_02.md#exercise) definition
+Read the instructions on the [Day 4 exercise](../day_04.md#exercise) definition
+
+HINT: Mutation objects are root GraphQL objects. They don’t have any associated "data" class. In such cases, the "resolver" class should be an annotated Spring controller.
 
 ### Requirements
 
-Java 1.8 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+Java 17 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
 
 ### Keep in mind
 

lessons/day_05/java/README.md

@@ -1,12 +1,21 @@
 # [A walk in GraphQL](../../../README.md)
 
-## Day 2 exercise - Java
+## Day 5 exercise - Java
 
-Read the instructions on the [Day 2 exercise](../day_02.md#exercise) definition
+Read the instructions on the [Day 5 exercise](../day_05.md#exercise) definition
+
+HINT:
+* Apply the following "hint" git patch: ".../a-walk-in-graphql/lessons/day_05/java/src/main/resources/Java_day_05_Interfaces_and_Unions_hint.patch".
+    * From command line: `git apply src/main/resources/Java_day_05_Interfaces_and_Unions_hint.patch`
+    * From IntelliJ IDEA:
+        * Open the "VCS" menu > "Apply Patch.."
+        * Select the ".../a-walk-in-graphql/lessons/day_05/java/src/main/resources/Java_day_05_Interfaces_and_Unions_hint.patch" file patch > OK    
+
+Now you need to complete the Mutation and Query resolvers with the required missing methods.
 
 ### Requirements
 
-Java 1.8 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+Java 17 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
 
 ### Keep in mind
 

lessons/day_06/java/README.md

@@ -1,12 +1,19 @@
 # [A walk in GraphQL](../../../README.md)
 
-## Day 2 exercise - Java
+## Day 6 exercise - Java
 
-Read the instructions on the [Day 2 exercise](../day_02.md#exercise) definition
+Read the instructions on the [Day 6 exercise](../day_06.md#exercise) definition
+
+
+HINTS:
+
+* You can split up your schema into more than one file to keep it organized.
+* The GraphQL Tools library works by processing GraphQL Schema files to build the correct structure and then wires special beans to this structure.
+* The Spring Boot GraphQL starter automatically finds these schema files, we just need to save these files with the extension `.graphqls` on the classpath (ex: inside `src/main/resources/graphql`).
 
 ### Requirements
 
-Java 1.8 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+Java 17 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
 
 ### Keep in mind
 

lessons/day_07/java/README.md

@@ -1,12 +1,26 @@
 # [A walk in GraphQL](../../../README.md)
 
-## Day 2 exercise - Java
+## Day 7 exercise - Java
 
-Read the instructions on the [Day 2 exercise](../day_02.md#exercise) definition
+Read the instructions on the [Day 7 exercise](../day_07.md#exercise) definition
 
 ### Requirements
 
-Java 1.8 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+Java 17 is required. Please look at [here](../../../setup/java.md#requirements) if you do not have it installed on your local environment. 
+
+
+
+HINTS: 
+
+* Exceptions (https://docs.spring.io/spring-graphql/docs/current/reference/html/#execution.exceptions)
+* Spring for GraphQL registers a DataFetcherExceptionHandler that provides default handling and enables the DataFetcherExceptionResolver contract.
+
+TODO Correct the patchs descriptions
+* Apply the following "hint" git patch to get an example of defending and informative error handling strategies: ".../a-walk-in-graphql/lessons/day_07/java/src/main/resources/Java_day_07_Error_Handling.patch".
+    * From command line: git apply src/main/resources/Java_day_07_Error_Handling.patch
+    * From IntelliJ IDEA:
+        * Open the "VCS" menu > "Apply Patch.."
+        * Select the ".../a-walk-in-graphql/lessons/day_07/java/src/main/resources/Java_day_07_Error_Handling.patch" file patch > OK
 
 ### Keep in mind