# 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=ankur@example.com, 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=ankur@example.com, 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=ankur@example.com, 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=ankur@example.com, 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