Java 27 and 26: runnable demos and captured output for every JEP, plus version lanes

Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
2026-09-21 15:08:50 +00:00
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+# One class file (javac 21 --release 21), four JVMs
+
+$ java -cp hub HubExamples      (JDK 21)
+    java.version = 21.0.12.1
+    CHECK ok   : record accessor: c.email()
+    CHECK ok   : record toString: Customer[id=1, [email protected], country=IN]
+    CHECK ok   : compact constructor rejects an email without @: Invalid email
+    CHECK ok   : area(Square(3)) == 9.0
+    CHECK ok   : area(Triangle(4, 5)) == 10.0
+    CHECK ok   : guard pattern: Circle(101) is a large circle
+    CHECK ok   : guard pattern: Circle(1) is a small circle
+    CHECK ok   : all 10,000 virtual-thread tasks completed before close() returned
+    CHECK ok   : and it took seconds, not the 1,000 s a serial loop needs (exact time is machine dependent, not printed)
+    CHECK ok   : Thread.ofVirtual().name(..).start(..) gives a virtual thread
+    CHECK ok   : List.getFirst() / getLast()
+    CHECK ok   : List.reversed(): [chris, brian, alex]
+    CHECK ok   : reversed() is a view, not a copy: it sees the element added afterwards
+    CHECK ok   : LinkedHashSet.getFirst() == 3, getLast() == 5
+
+$ java -cp hub HubExamples      (JDK 25)
+    java.version = 25.0.4.1
+    CHECK ok   : record accessor: c.email()
+    CHECK ok   : record toString: Customer[id=1, [email protected], country=IN]
+    CHECK ok   : compact constructor rejects an email without @: Invalid email
+    CHECK ok   : area(Square(3)) == 9.0
+    CHECK ok   : area(Triangle(4, 5)) == 10.0
+    CHECK ok   : guard pattern: Circle(101) is a large circle
+    CHECK ok   : guard pattern: Circle(1) is a small circle
+    CHECK ok   : all 10,000 virtual-thread tasks completed before close() returned
+    CHECK ok   : and it took seconds, not the 1,000 s a serial loop needs (exact time is machine dependent, not printed)
+    CHECK ok   : Thread.ofVirtual().name(..).start(..) gives a virtual thread
+    CHECK ok   : List.getFirst() / getLast()
+    CHECK ok   : List.reversed(): [chris, brian, alex]
+    CHECK ok   : reversed() is a view, not a copy: it sees the element added afterwards
+    CHECK ok   : LinkedHashSet.getFirst() == 3, getLast() == 5
+
+$ java -cp hub HubExamples      (JDK 26)
+    java.version = 26.0.2.1
+    CHECK ok   : record accessor: c.email()
+    CHECK ok   : record toString: Customer[id=1, [email protected], country=IN]
+    CHECK ok   : compact constructor rejects an email without @: Invalid email
+    CHECK ok   : area(Square(3)) == 9.0
+    CHECK ok   : area(Triangle(4, 5)) == 10.0
+    CHECK ok   : guard pattern: Circle(101) is a large circle
+    CHECK ok   : guard pattern: Circle(1) is a small circle
+    CHECK ok   : all 10,000 virtual-thread tasks completed before close() returned
+    CHECK ok   : and it took seconds, not the 1,000 s a serial loop needs (exact time is machine dependent, not printed)
+    CHECK ok   : Thread.ofVirtual().name(..).start(..) gives a virtual thread
+    CHECK ok   : List.getFirst() / getLast()
+    CHECK ok   : List.reversed(): [chris, brian, alex]
+    CHECK ok   : reversed() is a view, not a copy: it sees the element added afterwards
+    CHECK ok   : LinkedHashSet.getFirst() == 3, getLast() == 5
+
+$ java -cp hub HubExamples      (JDK 27)
+    java.version = 27
+    CHECK ok   : record accessor: c.email()
+    CHECK ok   : record toString: Customer[id=1, [email protected], country=IN]
+    CHECK ok   : compact constructor rejects an email without @: Invalid email
+    CHECK ok   : area(Square(3)) == 9.0
+    CHECK ok   : area(Triangle(4, 5)) == 10.0
+    CHECK ok   : guard pattern: Circle(101) is a large circle
+    CHECK ok   : guard pattern: Circle(1) is a small circle
+    CHECK ok   : all 10,000 virtual-thread tasks completed before close() returned
+    CHECK ok   : and it took seconds, not the 1,000 s a serial loop needs (exact time is machine dependent, not printed)
+    CHECK ok   : Thread.ofVirtual().name(..).start(..) gives a virtual thread
+    CHECK ok   : List.getFirst() / getLast()
+    CHECK ok   : List.reversed(): [chris, brian, alex]
+    CHECK ok   : reversed() is a view, not a copy: it sees the element added afterwards
+    CHECK ok   : LinkedHashSet.getFirst() == 3, getLast() == 5