How to get started with Java as quickly as possible

Apparently, Java 21 has some new things¹ to make it easier to get started with Java² right away.

So this is the ultimate blogpost of mine to get started quickly and easily.

Fair warning: I'm using the macos version of Java, so the directory structure might be a bit different compared to other Operating Systems.

Step 1. Download java

Go to https://jdk.java.net/21 and download the build you need.

Step 2. Unpack

Unpack the archive somewhere.

% tar zxvf Downloads/openjdk-21_macos-x64_bin.tar.gz

It will unpack in directory jdk-21.jdk.

Step 3. Write a small Java program

In this instance, we'll assume the file is called HelloWorld.java.

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

Step 4. Run the small Java program

% ~/jdk-21.jdk/Contents/Home/bin/java --enable-preview --source 21 ./HelloWorld.java
Note: ./HelloWorld.java uses preview features of Java SE 21.
Note: Recompile with -Xlint:preview for details.
Hello, world.

Congratulations, you've run your first Java Program!

The other way to do it, which admittedly is even quicker, is using the Java Playground³.

References

[1] JEP 445: Unnamed Classes and Instance Main Methods (Preview)

https://openjdk.org/jeps/445

[2] Paving the on-ramp

https://randomthoughtsonjavaprogramming.blogspot.com/2022/10/paving-on-ramp.html

[3] dev.java - Java Playground

https://dev.java/playground/