[Belisarius]

Java using something called a "CLASSPATH". It's an environmental variable that tells Java "this is where my files are". It will frequently look something like ".;c:/myjavafiles;c:/mylibs". It's a collection of system paths. For the most part, Netbeans will take care of it for you.

Additionally, you use something called "packaging". When you have a statement like

import javax.swing.*;

you're including all the files in the "javax.swing" package. Java looks through all the files in the CLASSPATH and picks out all the ones that start with

package javax.swing;

All Java programs start with the "static public void main(String[] args)" method. When you run a Java program, it executes the code in that method. While a Java program can be very large, with many classes and methods, the only one executed when a Java program is run is the "main" method. It's from that method that the rest of the code is called.