public Object someMethod(Object param) {
   return performLongCalculations();
}

private Object performLongCalculations() {
   // Здесь какие-то долгие вычисления/вызовы внешних сервисов и т.д.
}

public Object someMethod(final Object param) {
   SwingWorker<Object, Void> worker = new SwingWorker<Object, Void>() {
      @Override
      protected Object doInBackground() {
         return performLongCalculations(param);
      }

      @Override
      protected void done() {
         try {
            get();
         } catch (InterruptedException e) {

         }
         catch (ExecutionException e) {

         }
      }
   };
   worker.execute();
}