How does one access a method from an external jar at runtime?

Question

This is a continuation of the question posted in: How to load a jar file at runtime

I am uncertain as to how to continue to the method invocation level. From my und

Answer 1

Sample Program:

Project Printer:

public class Printer {

    public void display(String printtext)
    {
        System.out.println(printtext);
    }

}

This project is exported as Printer.jar.

Printer Class has method display() which takes string as input.

Invoking code:

       URL url = new URL("file:Printer.jar"); 
       URLClassLoader loader = new URLClassLoader (new URL[] {url});
       Class cl = Class.forName ("Printer", true, loader);
       String printString = "Print this";
       Method printit = cl.getMethod("display", String.class);
       Constructor ctor = cl.getConstructor(); //One has to pass arguments if constructor takes input arguments.
       Object instance = ctor.newInstance();
       printit.invoke(instance, printString);
       loader.close ();

Output: Print this