Load external class in Processing – Magic & Love Interactive

It is a short side project away from the OpenCV and Processing thread. In this example, I would like to see if I can load an external class within a Processing sketch. The structure of the program is:

Main program
TestLoad001

import java.lang.reflect.Method;
 
void setup() {
  size(640, 480);
}
 
void draw() {
  background(0);
}
 
void mousePressed() {
  MyLoader ldr = new MyLoader();
  Class myObj = ldr.load("MyTest");
  Object oo;
  try {
    oo = myObj.newInstance();
    println("Class name: " + oo.getClass().getName());
    Method m = oo.getClass().getMethod("ShowMe");
    println("Method name: " + m.getName());
    m.invoke(oo);
  } 
  catch (Exception e) {
    e.printStackTrace();
  }
}

Loader class
MyLoader (a subclass of ClassLoader)

import java.net.URL;
import java.net.URLConnection;
import java.io.ByteArrayOutputStream;
 
public class MyLoader extends ClassLoader {
 
  public MyLoader() {
    super();
  }
 
  public Class load(String _c) {
    try {
      String url = "file:" + dataPath(_c + ".class");
      URL addr = new URL(url);
      URLConnection conn = addr.openConnection();
 
      InputStream in = conn.getInputStream();
      ByteArrayOutputStream buf = new ByteArrayOutputStream();
      int num = in.read();
      while (num != -1) {
        buf.write(num);
        num = in.read();
      }
      in.close();
      byte [] data = buf.toByteArray();
 
      return defineClass("MyTest", data, 0, data.length);
    } 
    catch (Exception e) {
      e.printStackTrace();
    }
    return null;
  }
}

External class (compiled and placed inside the data folder)
MyTest

public class MyTest {
 
  public MyTest() {
    System.out.println("MyTest object instance created.");
  }
 
  public void ShowMe() {
    System.out.println("ShowMe method called.");
  }
}