Need help with java program

Hello! I need help with the following for my school project: 1. How do you make it so that if the person doesn't want to enter another input, the program will go to the next block of code? 2. How do you make it so that if they got a mistake at one input they can redo again? 3. How do you make sure that at the final print statement, it will only print the variables that the person entered?