Java compiling 101

gistfile1.txt

$ find .
.
./classes
./source
./source/local
./source/local/User1.java
./source/foreign
./source/foreign/User2.java
$
$ javac -d ./classes source/local/*.java source/foreign/*.java 
$
$ find .
.
./classes
./classes/local
./classes/local/User1.class
./classes/foreign
./classes/foreign/User2.class
./source
./source/local
./source/local/User1.java
./source/foreign
./source/foreign/User2.java
$
$ java -cp ./classes foreign.User2
User1 constructor
User2 constructor
$
$ cat source/local/User1.java 
package local;
public class User1 {
	public User1() {
		System.out.println("User1 constructor");
	}
}
$
$ cat source/foreign/User2.java 
package foreign;
import local.User1;
public class User2
		extends User1 {
	public static void main(final String[] args) {
		new User2();
	}
	public User2() {
		super();
		System.out.println("User2 constructor");
	}
}
$