I have a relatively large amount of code written without threads in mind. I am new at Java, and programming in general, so I am having a little trouble figuring out how to run the program I have built in threads without going back into all my classes and changing them to have a run() method. I can't even imagine how that's possible where I have multiple methods that are meant to be called separately from other classes.

I can't seem to find a way to create a thread for (every/a) new call to the code from the GUI. Say I have a method for inserting data into a database. The method is named and written. I could put a call to that class and method into my main, but what then when I want to call some other method? I have 25+ methods at least, and I can't really see my main class just being overloaded 25 times as "Best practice." Is there a way to create a thread and give it an object to handle dynamically, so to say?

In short: I want to use threads in my program without overloading my main, how do I do so?