Any java based open source tool like AutoIT?

Any java based open source tool like AutoIT to simulate windows functions

according to this java-and-macros-project, we can assume that not many projects will do that in Java.

the closest thing to consider as an answer to your question (even though I admit not 100%) are the following posts:

autoit-for-java

and

good-java-library-for-windows-application-automation

Check out Sikuli and Maveryx.

Sikulix is adding OCR-based automation and a GUI to Robot.java features. See on github