How to write own Method which waits until one statement is true

Hello im saw that many javaclasses have some sort of waitfor (like Process.waitFor() or Future.get()) Methods inside it, and i need to write Methods like that in a Future Program but with the difference, that it should check if a Method returns true or another Method (or Methods) has completed. Is there an elegant and not deprecated solve for this issue which doesnt contain some sort of Bruteforce? (like make an loop which infinitly checks an return statement)