Hypotenuse and name generator
SimpleTwo obj = new SimpleTwo();


is unnecessary because all your properties and methods of SimpleTwo are static, therefore creating an instance of SimpleTwo does nothing unless you have something in it that's not static. I would also guess that lines with code like obj.age give you a compiler warning because you should be using SimpleTwo.age since age is a static member.

I would also change the names of the classes and the methods to something more meaningful. firstMethod doesn't describe what it is for and technically it is the second method in your class