protected boolean verifyTargetClass (PsiClass targetClass) {
    if (targetClass.isInterface() && !PsiUtil.isAvailable(JavaFeature.EXTENSION_METHODS, targetClass)) {
      final Project project = getProject();
      if (ClassInheritorsSearch.search(targetClass, false).findFirst() == null) {
        final String message = JavaRefactoringBundle.message("0.is.an.interface.that.has.no.implementing.classes", DescriptiveNameUtil
          .getDescriptiveName(targetClass));

        Messages.showErrorDialog(project, message, myRefactoringName);
        return false;
      }

      final String message = JavaRefactoringBundle.message("0.is.an.interface.method.implementation.will.be.added.to.all.directly.implementing.classes",
                                                       DescriptiveNameUtil.getDescriptiveName(targetClass));

      final int result = Messages.showYesNoDialog(project, message, myRefactoringName,
                                                  Messages.getQuestionIcon());
      if (result != Messages.YES) return false;
    }

    return true;
  }
protected boolean verifyTargetClass (PsiClass targetClass)