How to avoid duplicate code with a helper-method for shared REST-operations like GET and DELETE

I have two methods

methodOne (e.g. for a GET on questionaire)
methodTwo (e.g. for a DELETE on questionaire)

Both have almost same lines of code.

IntelliJ also underlines the code and shows a warning:

duplicated code fragment

`methodOne`

@Override
public QuestionnaireDTO methodOne(long projectManagerId, long questionnaireId) {

    //the part I want to write into a helper method
    ProjectManager projectManager = projectManagerRepository.findById(projectManagerId).orElseThrow(
            () -> new ResourceNotFoundException("ProjectManager", "id", projectManagerId));

    Questionnaire questionnaire = questionnaireRepository.findById(questionnaireId).orElseThrow(() ->
            new ResourceNotFoundException("Questionnaire", "id", questionnaireId));

    if(!questionnaire.getProjectManager().getId().equals(projectManager.getId())){
        throw new QuestionnaireApiException(HttpStatus.BAD_REQUEST, "Questionnaire not belonging to Project Manager");
    }
    // end of helper method

    // return of methodOne 
    return mapToDto(questionnaire);
    
}

`methodTwo`

@Override
public QuestionnaireDTO methodTwo(long projectManagerId, long questionnaireId) {

    //the part I want to write into a helper method
    ProjectManager projectManager = projectManagerRepository.findById(projectManagerId).orElseThrow(
            () -> new ResourceNotFoundException("ProjectManager", "id", projectManagerId));

    Questionnaire questionnaire = questionnaireRepository.findById(questionnaireId).orElseThrow(() ->
            new ResourceNotFoundException("Questionnaire", "id", questionnaireId));

    if(!questionnaire.getProjectManager().getId().equals(projectManager.getId())){
        throw new QuestionnaireApiException(HttpStatus.BAD_REQUEST, "Questionnaire not belonging to Project Manager");
    }
    // end of helper method

    // return of methodTwo 
    return questionnaireRepository.delete(questionnaire);
    
}

Questions

I want to write the duplicated part of the code (enclosed in comments above) into a helper method. I want to avoid duplicate code but I'm not sure how to structure the helper method.

How can I achieve it?

Solution

You can actually just move the code 1:1 to a new method:

public QuestionnaireDTO methodTwo(long projectManagerId, long questionnaireId) {
    return mapToDto(findById(projectManagerId, questionnaireId));
}

public QuestionnaireDTO methodOne(long projectManagerId, long questionnaireId) {
    return questionnaireRepository.delete(findById(projectManagerId, questionnaireId));
}

private QuestionnaireDTO findById(long projectManagerId, long questionnaireId) {
    ProjectManager projectManager = projectManagerRepository.findById(projectManagerId).orElseThrow(
            () -> new ResourceNotFoundException("ProjectManager", "id", projectManagerId));

    Questionnaire questionnaire = questionnaireRepository.findById(questionnaireId).orElseThrow(() ->
            new ResourceNotFoundException("Questionnaire", "id", questionnaireId));

    if(!questionnaire.getProjectManager().getId().equals(projectManager.getId())){
        throw new QuestionnaireApiException(HttpStatus.BAD_REQUEST, "Questionnaire not belonging to Project Manager");
    }

    return questionnaire;
}