code: public void checkForModifications ()
      {
          for (Iterator<Map.Entry<String, ObservedResource>> it = _observed.entrySet().iterator();
                  it.hasNext(); ) {
              Map.Entry<String, ObservedResource> entry = it.next();
              ObservedResource resource = entry.getValue();
              if (resource.checkForModification(entry.getKey())) {
                  it.remove();
              }
          }
      }
docs: Checks all observed resources for changes to their {@link File#lastModified} properties,
  notifying their listeners if the files have been modified since the last call to this
  method.