Seems to work pretty well. I like this approach over things like GWT. Though creating a syntax error caused a bad exception:

  public class JavaFiddle
  {
      public static void main(String[] args)
      {
          x = 0;
      }
  }

Results in

  An exception has occurred in the compiler (1.8.0_131). 
  Please file a bug against the Java compiler via the Java bug reporting page (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com) for duplicates. Include your program and the following diagnostic in your report. Thank you.
  java.lang.NullPointerException