Bukkit

package mypack; // the package of your program

import com.rundumsweb.servers.bukkish.BukkishTask;
import com.rundumsweb.servers.bukkish.Session;

public class HelloWorld extends BukkishTask {

    // This constructor is needed
    public HelloWorld(LinkQueue lq, Session caller, String cmdLine) {
        super(lq, caller, cmdLine);
    }

    // The entry point
    public void run() {
        writeOut("Hello World");
        finish();  // To end the task
    }
}

mypack.HelloWorld

/mypack/HelloWorld.class
/mainClass.txt