ClassLoading?

[V Bose]

What would be the easiest way to run a java class located inside jar file from within a another running java program?

[Ben Souther]

Add the jar file to your classpath.
Import the class.
Then instanciate the class and call it's methods.

For example, if I had a jar file (foo.jar) with a foo.bar package.
In this package is a class named Thingy with a method called sayHello().

On Unix:
export CLASSPATH=$CLASSPATH:/jars/foo.jar

or on Windows:
set CLASSPATH=%CLASSPATH%;C:\jars\foo.jar

  
import foo.bar.Thingy;
 
public class Test{
    public static void main(String[] args){
        Thingy thingy = new Thingy;
        System.out.println(thingy.sayHello());
    }
 
}