Bump Java Version to 17/25 (#155)

* initial refactorings for Java 25 compatibility

spotbugs + pmd-plugin still need new releases that work on Java 25

* update CI config

* JDK builds pass

updates to the analysis plugins required some adjustments

* partially utilize Java 17 features

the benefit of records has not yet been looked at

* cleanups

Author: mtf90

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
     name: "Tests and Analysis (JDK: ${{ matrix.jdk }})"
     strategy:
       matrix:
-        jdk: [ 11, 17, 21 ]
+        jdk: [ 17, 21, 25 ]
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -56,7 +56,7 @@ jobs:
     needs: [ tests-and-analysis ]
     strategy:
       matrix:
-        jdk: [ 11, 17, 21 ]
+        jdk: [ 17, 21, 25 ]
         os: [ ubuntu-latest, windows-latest, macOS-latest ]
     runs-on: ${{ matrix.os }}
     steps:
@@ -99,7 +99,7 @@ jobs:
         uses: actions/setup-java@v3
         with:
           distribution: 'zulu'
-          java-version: 11
+          java-version: 17
       - name: Set up cache
         uses: actions/cache@v3
         with:
@@ -150,7 +150,7 @@ jobs:
         uses: actions/setup-java@v3
         with:
           distribution: 'zulu'
-          java-version: 11
+          java-version: 17
       - name: Set up cache
         uses: actions/cache@v3
         with:

CHANGELOG.md

@@ -12,7 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
-* LearnLib now requires Java 11 at runtime.
+* LearnLib now requires Java 17 at runtime.
 * The `generateTestWords` method of `AbstractTestWordEQOracle` now needs to be public.
 
 ### Fixed

README.md

@@ -42,7 +42,7 @@ Contributions -- whether it is in the form of new features, better documentation
 
 For simply using LearnLib you may use the Maven artifacts which are available in the [Maven Central repository][maven-central].
 It is also possible to download a bundled [distribution artifact][maven-central-distr] if you want to use LearnLib without Maven support.
-Note that LearnLib requires Java 11 (or newer) to build but still supports Java 8 at runtime.
+Note that LearnLib requires Java 17 (or newer) to build and run.
 
 #### Building development versions
 

algorithms/active/aaar/src/main/java/de/learnlib/algorithm/aaar/abstraction/AbstractAbstractionTree.java

@@ -132,8 +132,7 @@ public Collection<CI> getRepresentativeSymbols() {
 
     @Override
     public Collection<Node> getOutgoingEdges(Node node) {
-        if (node instanceof InnerNode) {
-            final InnerNode<?, ?> n = (InnerNode<?, ?>) node;
+        if (node instanceof InnerNode<?, ?> n) {
             return Arrays.asList(n.equalsNext, n.otherNext);
         }
 
@@ -155,8 +154,7 @@ public Collection<Node> getNodes() {
 
         while (!nodes.isEmpty()) {
             final Node n = nodes.poll();
-            if (n instanceof InnerNode) {
-                final InnerNode<?, ?> in = (InnerNode<?, ?>) n;
+            if (n instanceof InnerNode<?, ?> in) {
                 result.add(in);
                 nodes.add(in.equalsNext);
                 nodes.add(in.otherNext);
@@ -177,11 +175,9 @@ public VisualizationHelper<Node, Node> getVisualizationHelper() {
             public boolean getNodeProperties(Node node, Map<String, String> properties) {
                 super.getNodeProperties(node, properties);
 
-                if (node instanceof InnerNode) {
-                    final InnerNode<?, ?> n = (InnerNode<?, ?>) node;
+                if (node instanceof InnerNode<?, ?> n) {
                     properties.put(NodeAttrs.LABEL, n.prefix + ", " + n.suffix);
-                } else if (node instanceof Leaf) {
-                    final Leaf<?, ?> l = (Leaf<?, ?>) node;
+                } else if (node instanceof Leaf<?, ?> l) {
                     properties.put(NodeAttrs.LABEL, String.format("Abs.: '%s'%nRep.: '%s'", l.abs, l.rep));
                 }
 
@@ -192,8 +188,7 @@ public boolean getNodeProperties(Node node, Map<String, String> properties) {
             public boolean getEdgeProperties(Node src, Node edge, Node tgt, Map<String, String> properties) {
                 super.getEdgeProperties(src, edge, tgt, properties);
 
-                if (src instanceof InnerNode) {
-                    final InnerNode<?, ?> n = (InnerNode<?, ?>) src;
+                if (src instanceof InnerNode<?, ?> n) {
                     if (n.equalsNext == tgt) {
                         properties.put(EdgeAttrs.LABEL, "== " + n.out);
                     } else {

algorithms/active/aaar/src/main/java/de/learnlib/algorithm/aaar/abstraction/Node.java

@@ -17,7 +17,7 @@
 
 import net.automatalib.word.Word;
 
-class Node {
+public class Node {
 
     static class InnerNode<CI, D> extends Node {
 

algorithms/active/aaar/src/test/java/de/learnlib/algorithm/aaar/explicit/ModuloInitialAbstraction.java

@@ -40,14 +40,11 @@ public String getAbstractSymbol(CI c) {
 
     @Override
     public CI getRepresentative(String a) {
-        switch (a) {
-            case "even":
-                return alphabet.getSymbol(0);
-            case "odd":
-                return alphabet.getSymbol(1);
-            default:
-                throw new IllegalArgumentException("Unknown symbol: " + a);
-        }
+        return switch (a) {
+            case "even" -> alphabet.getSymbol(0);
+            case "odd" -> alphabet.getSymbol(1);
+            default -> throw new IllegalArgumentException("Unknown symbol: " + a);
+        };
     }
 
     @Override

algorithms/active/adt/src/main/java/de/learnlib/algorithm/adt/api/ADTExtender.java

@@ -24,6 +24,7 @@
  * Interface for configuration objects that specify how to finalize the temporary splitter given by regular
  * counterexample decomposition.
  */
+@FunctionalInterface
 public interface ADTExtender {
 
     /**

algorithms/active/adt/src/main/java/de/learnlib/algorithm/adt/api/LeafSplitter.java

@@ -22,6 +22,7 @@
  * Interface for configuration objects that specify how to split the ADT leaf of a hypothesis state that needs
  * refinement.
  */
+@FunctionalInterface
 public interface LeafSplitter {
 
     /**

algorithms/active/adt/src/main/java/de/learnlib/algorithm/adt/api/SubtreeReplacer.java

@@ -25,6 +25,7 @@
 /**
  * Interface for configuration objects that specify how nodes of the current ADT should be replaced.
  */
+@FunctionalInterface
 public interface SubtreeReplacer {
 
     /**

algorithms/active/adt/src/main/java/de/learnlib/algorithm/adt/config/model/ADSCalculator.java

@@ -22,6 +22,7 @@
 import net.automatalib.alphabet.Alphabet;
 import net.automatalib.automaton.transducer.MealyMachine;
 
+@FunctionalInterface
 public interface ADSCalculator {
 
     <S, I, O> Optional<ADTNode<S, I, O>> compute(MealyMachine<S, I, ?, O> hypothesis,