java - findbyID returns optional . setting this object to another object cause error

Question

    
    public String addStudyProgram(){
        
        Optional<StudyProgram> program = studyProgramRepository.findById(1);        

            Student student = new Student();        
            student.setStudentName("Mushashi");
            
            student.setProgram(program);    // error The method setProgram(StudyProgram) in the type Student is not applicable for the arguments (Optional<StudyProgram>)   
        
        return "Done";
    }

student and program are DTO , if i change setProgram(StudyProgram) method to setProgram(Optional) then it interfere with database scheme. what will be the solution ?

Answer 1

program is Optional, use program.get() for getting object value : student.setProgram(program.get()); Before make get(), you should check if we have a result: if(program.isPresent()) { student.setProgram(program.get());}

Answer 2

Optional<Object> is not the actual Object. You can use obj.get() if you're sure that the value is present in the Optional. To avoid such an occurrence and be null safe, you can use obj.orElse(defaultValue) which will return the defaultValue as an Object instance.