Magic

Decompiled class X$Y

localhost:main dmitry$ javap -p -c X\$Y
Compiled from "X.scala"
public class X$Y {
  public X$Y();
    Code:
       0: aload_0
       1: invokespecial #9                  // Method java/lang/Object."<init>":()V
       4: return
}

Decompiled object X$Y

localhost:main dmitry$ javap -p -c X\$Y\$
Compiled from "X.scala"
public class X$Y$ {
  public static final X$Y$ MODULE$;

  private final long y;

  public static {};
    Code:
       0: new           #2                  // class X$Y$
       3: invokespecial #12                 // Method "<init>":()V
       6: return

  public long y();
    Code:
       0: aload_0
       1: getfield      #17                 // Field y:J
       4: lreturn

  public X$Y$();
    Code:
       0: aload_0
       1: invokespecial #19                 // Method java/lang/Object."<init>":()V
       4: aload_0
       5: putstatic     #21                 // Field MODULE$:LX$Y$;
       8: aload_0
       9: invokestatic  #26                 // Method java/lang/System.nanoTime:()J
      12: putfield      #17                 // Field y:J
      15: return
}

Main.java

    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException, InstantiationException, InterruptedException, NoSuchFieldException {
        Class<?> cls = X$Y$.class;
        Constructor<?> constructor = cls.getConstructor();
        Field module = cls.getField("MODULE$");
        Method y = cls.getMethod("y");
        System.out.println(y.invoke(module.get(null)));
        Object o = constructor.newInstance();
        System.out.println(y.invoke(module.get(null)));
        Thread.sleep(10);
        Object o1 = constructor.newInstance();
        System.out.println(y.invoke(module.get(null)));

        System.out.println(y.invoke(o));
        System.out.println(y.invoke(o1));
    }

X.scala

class X {

}

object X {
  val x = "test"

  class Y {

  }

  object Y {
    val y = System.nanoTime()
  }
}