I have one question, when you want to add a game round in a java game, how do you do it, do you use the round().method or do you simply put (round++) + 1?

There's nowhere near enough context there to answer the question. What are round() and round for example?

Pretty much what james said but
if round is an integer and that's what keeps count of the rounds, increasing it should work

what I mean it when you are programming a game in java,you want to add another rounds to each level. the java game/program that I am building need to have game rounds for each level.

it is a multiplication math game, level 2 need to have 4 rounds which would rounds off to 12 questions which should be randonly generated each time the program launch, so I need to know how to codes the rounds into the games so that i can go into the next questions

Why not just a simple
int roundNumber = 0;
then increment it as each round is completed:

james cherril thank u very much and I have another question, in the game I have to create level whether it is easy, medium or hard, how do I do that, do I have to prompt for it or do i have to do a for loop because i did it in a for loop and it was only println easy how do i ask the user if they want to play either the easy, medium or hard game level

Just display a message and read the reply - it's no different from any other interaction with the user.