Hi All,
I've been programming in C++ for a few years and feel fairly comfortable
there. But recently I switched over to Java because, quite frankly, it's
easier. But I have a couple of questions about classes that I am hoping someone
will take the time to answer. I would really appreciate it.

1) I know that most serious Java programs use multiple class files. Why?
Is this simply to prevent the existance of a huge, slow, and virtually unrunnable
single class?

2) If not, under what circumstances do I need to use multiple class files.
For instance, I am writing a small telnet program in Java. If the user
clicks "Connect" and hasn't entered any server information I will display
a hand made dialog box telling him to go back and enter some information.
Should I put the code for this dialog box in a seperate class file?

3) How do I call methods in an external class file? Is it as simple as a
class.method() call?

I know these are really newbie questions and is probably wasting everyone's
time but I can't seem to find any answers anywhere else. Again, thanks in
advance for your answers.