Concurrent class initialization

ClassInit.java

import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;

public class ClassInit {
  static final int CLASSLOADERS = Integer.getInteger("classloaders", 3);
  static final int THREADS = Integer.getInteger("threads", 3);

  static class MyClassLoader extends URLClassLoader {
    public MyClassLoader() {
      super(new URL[] { ClassInit.class.getProtectionDomain().getCodeSource().getLocation() });
    }
    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
      if (name.startsWith("ClassInit$Singleton") || name.startsWith("ClassInit$UseSingleton")) {
        Class<?> c = findClass(name);
        if (resolve) {
          resolveClass(c);
        }
        return c;
      }
      else {
        return super.loadClass(name, resolve);
      }
    }
  }

  static class Singleton {
    public static Singleton singleton;
    static {
      new Singleton();
    }
    private Singleton() {
      singleton = this;
    }

    public int min(int i, int j) {
      return Math.min(i, j);
    }
  }
  static class UseSingleton {
    static volatile boolean start = false;
    public static void useSingleton() {
      int THREADS = Integer.getInteger("threads", 3);
      for (int i = 0; i < THREADS; i++) {
        final int j = i;
        new Thread() {
          public void run() {
            while (!start) Thread.onSpinWait();
            Singleton.singleton.min(j, THREADS);
          }
        } . start();
      }
      start = true;
    }
  }

  public static void main(String args[]) throws Exception {
    for (int i = 0; i < THREADS; i++) {
      new Thread() {
        public void run() {
          for (int i = 0; i < CLASSLOADERS; i++) {
            try {
              Method get = new MyClassLoader().loadClass("ClassInit$UseSingleton").getDeclaredMethod("useSingleton");
              get.setAccessible(true);
              get.invoke(null);
            } catch (Exception e) {
              throw new Error(e);
            }
          }
        }
      } . start();
    }
  }
}