Java 25: Module import declarations (JEP 511)

JavaReleases/src/main/java/pl/mperor/lab/java/JavaBaseImport.java

@@ -4,7 +4,7 @@
 
 class JavaBaseImport {
 
-    private final List<String> listFromUtilPackage = List.of("a", "b", "c");
-    private final File fileFromIoPackage = new File("file.txt");
+    final List<String> listFromUtilPackage = List.of("a", "b", "c");
+    final File fileFromIoPackage = new File("file.txt");
 
 }

JavaReleases/src/main/java/pl/mperor/lab/java/JavaDesktopImportAmbiguity.java

@@ -0,0 +1,15 @@
+package pl.mperor.lab.java;
+
+import module java.desktop;
+import java.util.List; // single-type import wins over the module import below, resolving List as java.util.List
+
+/// Demonstrates a caveat called out by JEP 511: `import module java.desktop` imports every package
+/// exported by java.desktop (including `java.awt`, which defines `java.awt.List`) and, because
+/// java.desktop is not java.base, also every package exported by java.base (including `java.util`,
+/// which defines `java.util.List`). The bare name `List` is therefore ambiguous between the two
+/// types; without the single-type import above, this file would not compile.
+class JavaDesktopImportAmbiguity {
+
+    final List<String> names = List.of("John Doe", "Jane Doe");
+
+}

JavaReleases/src/test/java/pl/mperor/lab/java/Java25.java

@@ -148,4 +148,20 @@ public void testScopedValueHasNoSetUnlikeThreadLocal() {
         Assertions.assertFalse(USER.isBound());
     }
 
+    @Test
+    public void testModuleImportBringsInAllExportedPackagesOfJavaBase() {
+        var demo = new JavaBaseImport();
+        // List.of(...) (java.util) and new File(...) (java.io) are two different java.base packages,
+        // both resolved inside JavaBaseImport.java by its single `import module java.base;` declaration
+        Assertions.assertEquals(java.util.List.of("a", "b", "c"), demo.listFromUtilPackage);
+        Assertions.assertEquals("file.txt", demo.fileFromIoPackage.getName());
+    }
+
+    @Test
+    public void testModuleImportAmbiguityResolvedBySingleTypeImport() {
+        var demo = new JavaDesktopImportAmbiguity();
+        // proof that `names` really is java.util.List, not java.awt.List, see JavaDesktopImportAmbiguity.java
+        Assertions.assertEquals(java.util.List.of("John Doe", "Jane Doe"), demo.names);
+    }
+
 }