Java Development Kit (JDK)
As of 0.6.5, the new Plugin API currently uses JDK 20. It's shipped with the game, so it's recommendable to use it from the game directoy: You can find it in the game folder under _New Version/Data/Java/JDK
Alternatively you can download it here: https://jdk.java.net/20/
Integrated Development Environment (IDE)
While it's possible to create plugins using a text editor, it's highly recommendable to use an IDE (integrated development environment). It provides code completion, can show documentations and also enables you to compile the plugins easily.
This is an overview of some popular IDE's:
Getting started
The game is already shipped with the API library (jar) and the according Javadoc - both can be found in the game directory under _New Version/Data/SDK
If you use the API from the game directory, your IDE will always use the latest API automatically (everytime the game gets updated).
This link contains an online version of the latest Javadoc: https://javadoc.rising-world.net
