Tuesday, March 12, 2019

Unexpected behavior


I'm developing a Chemical drawing tool and have been progressing steadily with a lot of difficulties. My technology stack is Java 8, GWT 2.8.2, GMD 2.x, Eclipse Photon, running on a MacBook Pro, and Chrome | Firefox | Opera for testing. A limited functioning pilot is running at http://peruselab.com.

I just ran into a trouble that I couldn't figure out on my own. Below are the relevant snippets of code that's causing trouble. The call (1) ActionHandlerMap.getHandler(action) is expected to return an instance of PeruseEventHandler. I expect the sequence of execution to be 1, 2, & 3. However, upon returning from 2 (verified with the debugger) I see the control going to 4 (screen clip 1) followed by throwing an exception (screen clip 2). Any idea what could be wrong? Your help will be greatly appreciated.


  PeruseEventHandler eventHandler = ActionHandlerMap.getHandler(action); // 1

  Globals.currentShape = eventHandler.handle(null, null); // 3

public class ActionHandlerMap {

  public static final Map<Action, PeruseEventHandler> ACTION_HANDLER_MAP = new HashMap<>();

  static {

    ACTION_HANDLER_MAP.put(Action.DRAW_SINGLE_BOND, new SingleBondDrawingHandler());


  public static PeruseEventHandler getHandler(Action anAction) {

    return ACTION_HANDLER_MAP.get(anAction); // 2



class Globals {

  public static Action action;

  public static Shape currentShape; // 4


Enter code here...

Screen Shot 2019-03-12 at 5.36.35 PM.png

Screen clip 1

Screen Shot 2019-03-12 at 5.40.52 PM.png

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