JAVA source files

A java source file can contain more than one class. Not more than one of these classes may be declared public.
If the source file contains a public class, then the name of the source file must be the name of this public class with a .java suffix.

The java compiler creates a .class file for each class found in the source file.

A java source file consists of three parts:

• Optional package definition (using the package keyword)
• Zero, one or more import statements.
• class and interface definitions.

These parts must be in order. That is, the following example is an invalid source file because the import statement occurs before the package statement:

import java.util.*;

package ch.adp-gmbh.some_thing;

class XYZ {
  // ...
}

This implies also that an empty source file is actually a valid source file. Most probably, however, it won't make any sense to anyone.