private static void removeOldArtifacts(List<URI> existingURIs) {
   for (IndexRow row : IndexUtil.INSTANCE.getIndex()) {
     URI rowURI = URI.createURI(row.getPhyURI());
     if (rowURI != null && rowURI.isPlatformPlugin()) {
       if (!existingURIs.contains(rowURI)) {
         IndexUtil.INSTANCE.removeArtifact(rowURI);
       }
     }
   }
 }
 /**
  * Runs the action.
  *
  * @param action the action proxy that handles the presentation portion of the action
  */
 public void run(IAction action) {
   for (IndexRow row : IndexUtil.INSTANCE.getIndex()) {
     URI uri = ResourceUtil.uriFrom(row.getPhyURI());
     IFile file = ResourceUtil.fileFor(uri);
     if (file == null || !file.exists()) {
       IndexUtil.INSTANCE.removeArtifact(row);
     }
   }
   IndexUtil.INSTANCE.commitIndex();
 }