How can i write custom keyword in java?

Mention the steps to write custom keyword in java,because katalon has only groovy scrpit page and also i need to know how to call that custom keyword?

Ok so where in the Tests Explorer do I do this? When I create a new keyword the file is filename.groovy.

and the code starts:

public class filename {


Go through this below code

//This id deceleration
void clickOkBtn()’

//we call the keyword/method in test case as
Custom.Keyword. (Note here after . you will find the custom keyword which you declared)

The @Keyword should be mentioned and the before calling it should be saved