MyMatchEngine extends GenericMatchEngine {

...

}

  static boolean isDifferent(EObject left, EObject right) {
    DiffModel diff = null;
    MatchModel match = null;
    Map<String, Object> options = new HashMap<String, Object>();
    // options.put(MatchOptions.OPTION_IGNORE_XMI_ID, new Boolean(true));
    try {

      // MatchEngineRegistry.INSTANCE. blabla

      // Reguires a List<MatchEngineDescriptor> engines..
      IMatchEngineSelector selector = somehow...;
      selector.selectMatchEngine(engines);
      MatchService.setMatchEngineSelector(selector);


      // doContentMatch from current model and down
      match = MatchService.doContentMatch(left, right, options);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
...

      MyMatcherEngine myEngine = new MyMatcherEngine();
      myEngine.contentMatch(leftObject, rightObject, optionMap)

    DiffModel diff = null;
    MatchModel match = null;
    Map<String, Object> options = new HashMap<String, Object>();
    // my own impl. that overrides the isSimilar method.
    MyMatcherEngine myEngine = new MyMatcherEngine();
    match = myEngine.contentMatch(left, right, options);
    diff = DiffService.doDiff(match, false);
    List<DiffElement> differences1 = new ArrayList<DiffElement>(diff.getOwnedElements());
    System.out.println(differences1.size());

public class MyDiffEngine extends GenericDiffEngine {

        @Override
	public DiffModel doDiff(MatchModel match, boolean threeWay) {
              
          

        }
}

	public DiffModel doDiff(MatchModel match, boolean threeWay) {
		matchCrossReferencer = new EcoreUtil.CrossReferencer(match) {
			private static final long serialVersionUID = 1L;

			/** initializer. */
			{
				crossReference();
			}
		};
		final DiffModel result = DiffFactory.eINSTANCE.createDiffModel();
		result.getLeftRoots().addAll(match.getLeftRoots());
		result.getRightRoots().addAll(match.getRightRoots());
		result.getAncestorRoots().addAll(match.getAncestorRoots());
		DiffGroup diffRoot = null;

		if (threeWay) {
			diffRoot = doDiffThreeWay(match);
		} else {
			diffRoot = doDiffTwoWay(match);
		}
		result.getOwnedElements().add(diffRoot);

		return result;
	}

    MyMatcherEngine myEngine = new MyMatcherEngine();
    match = myEngine.contentMatch(left, right, options);
    
    MyDiffEngine diffEngine = new MyDiffEngine();
    diff  = diffEngine.doDiff(match, false);
    List<DiffElement> differences1 = new ArrayList<DiffElement>(diff.getOwnedElements());
    System.out.println(differences1.size());