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Comment by nayuki | Hacker News Reader

Java SE 11 (Sep 2018) introduced the ability to run source files directly. So instead of the old `javac Main.java && java Main`, you can do `java Main.java`. https://openjdk.org/projects/jdk/11/ , https://openjdk.org/jeps/330

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Furthermore, there's ongoing work ([0] and related JEPs) to allow running single Java files without an enclosing class and the static main method:

  void main() {
      System.out.println("Hello, World!");
  }

This is currently (as of JDK 24) under preview, so such a file needs to be run with "--enable-preview". E.g.

  $ java --enable-preview HelloWorld.java
  Hello, World!

[0] https://openjdk.org/jeps/445

With the latest EA release (EA 24) of JDK 25 [1], you no longer need the `--enable-preview`. You can also simplify the println to:

  void main() {
      IO.println("Hello, World!");
  }

JEP 445 has been followed by JEP 512 which contained minor improvements and finalizes the feature [2].

If you want to use 3rd-party libraries, I highly recommend trying JBang [3].

[1] https://jdk.java.net/25/release-notes

[2] https://openjdk.org/jeps/512

[3] https://www.jbang.dev

Hmmm... Disappointing that the static methods are no longer imported as of JEP 512. I thought that was the whole point of the new IO class. If we can't write "println" we might as well just write "System.out.println".

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