Specify Java 21 instead of 17

Signed-off-by: Andrew Helwer <[email protected]>

Author: ahelwer

.github/workflows/ci.yml

@@ -18,11 +18,11 @@ jobs:
         uses: actions/checkout@v4
         with:
           submodules: true
-      - name: Install JDK 17
+      - name: Install JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: adopt
-          java-version: 17
+          java-version: 21
       - name: Install SBT
         uses: sbt/setup-sbt@v1
       - name: Validate 2-scanning

1-start/wikipage.txt

@@ -39,7 +39,7 @@ There are two good reasons for this:
   - The high-quality free online textbook //[[https://craftinginterpreters.com/contents.html|Crafting Interpreters]]// by Robert Nystrom uses Java, and this tutorial is a simple TLA⁺-themed wrapper around its concepts. That book states its own reasons for using Java, which you can read.
 
 You will need to install the [[https://adoptium.net/|Java Development Kit]] appropriate for your system.
-This tutorial uses the Java 17 [[https://openjdk.org/jeps/395|records]] feature for terse definition of dataclasses, so you must install JDK 17 or higher.
+This tutorial requires Java 21 or higher, for the Java 17 [[https://openjdk.org/jeps/395|records]] feature and the Java 21 [[https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/SequencedCollection.html#reversed()|''reversed()'']] method.
 While all code artifacts can be produced entirely by reading this tutorial, if you get out of sync you can find working implementations in [[https://github.com/tlaplus/devkit|this git repository]].
 
 The tutorial has you construct the TLA⁺ tools from the bottom up.

10-closures/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

2-scanning/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

3-expressions/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

4-evaluation/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

5-statements/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

6-jlists/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

7-operators/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run

8-actions/README.md

@@ -5,7 +5,7 @@ You can see the expected state of the source code after the tutorial in the [src
 Unit tests (not covered in the tutorial) are in the [test](test) directory.
 
 ## Dependencies
-- [OpenJDK 17+](https://adoptium.net/)
+- [OpenJDK 21+](https://adoptium.net/)
 - [sbt (simple build tool)](https://www.scala-sbt.org/)
 
 ## Build, test, run