Add jep512 module: compact source files and instance main methods on JDK 25 and 27

Runnable sources, broken examples and captured transcripts for the ankurm.com JEP 512 article, including the measured launch order and a private-constructor difference between 25 and 27. Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01TF9JWFvJSNm6HVzswzZU5a
2026-09-24 10:32:47 +00:00
parent 6b5a918278
commit e0cb6e83e2
34 changed files with 490 additions and 0 deletions
@@ -0,0 +1,68 @@
+$ java broken/NoMain.java     (JDK 25)
+broken/NoMain.java:1: error: compact source file does not have main method in the form of void main() or void main(String[] args)
+void greet() { IO.println("hi"); }
+^
+1 error
+error: compilation failed
+
+$ java broken/NoIoPrefix.java     (JDK 25)
+broken/NoIoPrefix.java:2: error: cannot find symbol
+    println("hello");
+    ^
+  symbol:   method println(String)
+  location: class NoIoPrefix
+1 error
+error: compilation failed
+
+$ java broken/NotInJavaBase.java     (JDK 25)
+broken/NotInJavaBase.java:2: error: cannot find symbol
+    HttpClient client = HttpClient.newHttpClient();
+    ^
+  symbol:   class HttpClient
+  location: class NotInJavaBase
+broken/NotInJavaBase.java:2: error: cannot find symbol
+    HttpClient client = HttpClient.newHttpClient();
+                        ^
+  symbol:   variable HttpClient
+  location: class NotInJavaBase
+2 errors
+error: compilation failed
+
+$ java broken/WithPackage.java     (JDK 25)
+broken/WithPackage.java:1: error: compact source file should not have package declaration
+package demo;
+^
+1 error
+error: compilation failed
+
+$ javac -d out broken/Other.java broken/Target.java     (JDK 25; Target.java is a compact file)
+broken/Other.java:2: error: Target is abstract; cannot be instantiated
+    Target t = new Target();
+               ^
+broken/Other.java:3: error: cannot find symbol
+    t.main();
+     ^
+  symbol:   method main()
+  location: variable t of type Target
+2 errors
+
+$ java broken/Other.java     (JDK 25; source launcher, Target.java sits next to it)
+broken/Other.java:2: error: Target is abstract; cannot be instantiated
+    Target t = new Target();
+               ^
+1 error
+error: compilation failed
+
+$ java broken/WrongParam.java     (JDK 25)
+broken/WrongParam.java:1: error: compact source file does not have main method in the form of void main() or void main(String[] args)
+void main(int count) { IO.println("count = " + count); }
+^
+1 error
+error: compilation failed
+
+$ java broken/PrivateMain.java     (JDK 25)
+error: can't find main(String[]) or main() method in class: PrivateMain
+
+$ java broken/CtorWithArgs.java     (JDK 25)
+error: can't find no argument constructor in class: CtorWithArgs
+