Question: when I use `Thread.sleep();`, it pauses my entire program. Is there anything that pauses one class without using multithreading?

Answer: 
I think you're confusing some concepts here. Classes and Objects do not run. Threads run, and what they run are the instructions (code) defined by classes and objects.

So no, you cannot pause a Class or Object, only a Thread. Moreover, if your application is single threaded, then you only have a "main" thread, and if you pause that thread then your whole application will pause.
No. You cannot. You have the main thread . Sleep will pause it. If you want stop run something without affect the main thread you need to fork it from the main thread , by use addiotnal thread