Add Java 15 test class ...

README.md

@@ -26,5 +26,6 @@ This project includes unit tests for key functionalities introduced in each Java
 - [Java 12](src/test/java/pl/mperor/lab/java/Java12.java)
 - [Java 13](src/test/java/pl/mperor/lab/java/Java13.java)
 - [Java 14](src/test/java/pl/mperor/lab/java/Java14.java)
+- [Java 15](src/test/java/pl/mperor/lab/java/Java15.java)
 
 For detailed examples and tests of each feature, please refer to the individual source files linked above.

src/main/java/pl/mperor/lab/java/sealed/AlsoFinal.java

@@ -0,0 +1,4 @@
+package pl.mperor.lab.java.sealed;
+
+public final class AlsoFinal extends AlsoSealed {
+}

src/main/java/pl/mperor/lab/java/sealed/AlsoSealed.java

@@ -0,0 +1,8 @@
+package pl.mperor.lab.java.sealed;
+
+public sealed class AlsoSealed implements Sealed permits AlsoFinal {
+
+    public String alsoSealedMethod() {
+        return "sealed";
+    }
+}

src/main/java/pl/mperor/lab/java/sealed/Final.java

@@ -0,0 +1,8 @@
+package pl.mperor.lab.java.sealed;
+
+public final class Final implements Sealed {
+
+    public String finalMethod() {
+        return "final";
+    }
+}

src/main/java/pl/mperor/lab/java/sealed/NonSealed.java

@@ -0,0 +1,8 @@
+package pl.mperor.lab.java.sealed;
+
+public non-sealed class NonSealed implements Sealed {
+
+    public String nonSealedMethod() {
+        return "non-sealed";
+    }
+}

src/main/java/pl/mperor/lab/java/sealed/Sealed.java

@@ -0,0 +1,9 @@
+package pl.mperor.lab.java.sealed;
+
+public sealed interface Sealed permits AlsoSealed, NonSealed, Final {
+
+    default String sealedMethod() {
+        return "sealed";
+    }
+
+}

src/test/java/pl/mperor/lab/java/Java15.java

@@ -0,0 +1,33 @@
+package pl.mperor.lab.java;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import pl.mperor.lab.java.sealed.*;
+
+/**
+ * Java 15 (September 2020)
+ */
+public class Java15 {
+
+    @Test
+    public void testSealedClasses() {
+        Assertions.assertTrue(Sealed.class.isSealed());
+        Assertions.assertFalse(NonSealed.class.isSealed());
+        Assertions.assertFalse(Final.class.isSealed());
+        Assertions.assertTrue(AlsoSealed.class.isSealed());
+        Assertions.assertFalse(AlsoFinal.class.isSealed());
+
+        Assertions.assertEquals("final", switchSealed(new Final()));
+        Assertions.assertEquals("non-sealed", switchSealed(new NonSealed()));
+        Assertions.assertEquals("sealed", switchSealed(new AlsoSealed()));
+    }
+
+    private String switchSealed(Sealed sealed) {
+        return switch (sealed) {
+            case AlsoSealed a -> a.alsoSealedMethod();
+            case Final f -> f.finalMethod();
+            case NonSealed ns -> ns.nonSealedMethod();
+        };
+    }
+
+}