class XLoader extends ClassLoader {

    // карта отображения имен классов на файлы .class, где хранятся их определения
    HashMap<String, String> mappings;

    XLoader(HashMap mappings) {
        this.mappings = mappings;
    }


    public synchronized Class loadClass(String name) throws ClassNotFoundException {
        try {
            // важно!
            // приоритет отдан именно загрузке с помощью встроенного загрузчика

            if (!mappings.containsKey(name)) {
                System.out.println("loadClass (" + name + ") with parent classloader");
                return super.findSystemClass(name);
            }
            System.out.println("loadClass (" + name + ") with XLoader");
            String fileName = mappings.get(name);
            FileInputStream fin = new FileInputStream(fileName);
            byte[] bbuf = new byte[(int) (new File(fileName).length())];
            fin.read(bbuf);
            fin.close();
            return defineClass(name, bbuf, 0, bbuf.length);

        } catch (IOException e) {
            e.printStackTrace();
            throw new ClassNotFoundException(e.getMessage(), e);
        }
    }
}

public class SexyClassForLoader implements ISexyInterface {

    public static String stat_foo = "hello stat_foo";


    static {
        System.out.println("SexyClassForLoader$$static");
    }


    public SexyClassForLoader() {
        System.out.println("SexyClassForLoader$$init");
    }


    public static String getStatFoo() {
        return stat_foo;
    }


    public String getSimpleFoo() {
        return simple_foo;
    }
    public String simple_foo = "hello simple_foo";


    public void makeBar() {
        System.out.println("make bar");
    }

}

public interface ISexyInterface {

    public void makeBar ();

}

        HashMap<String, String> mappings = new HashMap();
        mappings.put("sur.che.SexyClassForLoader", "D:\\java_things\\custom-classloader\\out\\production\\custom-classloader1\\sur\\che\\SexyClassForLoader.class");
        // if comment this line you will see
        mappings.put("sur.che.ISexyInterface", "D:\\java_things\\custom-classloader\\out\\production\\custom-classloader1\\sur\\che\\ISexyInterface.class");

        XLoader xloa = new XLoader(mappings);
        Class sexy_cla = xloa.loadClass("sur.che.SexyClassForLoader");
        System.out.println("class was loaded with " + sexy_cla.getClassLoader());

        Object sexy_ob = sexy_cla.newInstance();
        System.out.println(sexy_ob.getClass().getClassLoader());
        System.out.println(ISexyInterface.class.getClassLoader());
        Thread.sleep(100);
        ISexyInterface local_sexy = (ISexyInterface) sexy_ob;
        local_sexy.makeBar();

mappings.put("sur.che.ISexyInterface", "D:\\java_things\\custom-classloader\\out\\production\\custom-classloader1\\sur\\che\\ISexyInterface.class");

mappings.put("sur.che.ISexyInterface", "D:\\java_things\\custom-classloader\\out\\production\\custom-classloader1\\sur\\che\\ISexyInterface.class");