Java Strategy Pattern - unchecked call as member of type

I had a service that I was doing a lot of if/else statements so I found that using Strategy Pattern could help me a lot.

I am working with Mongo and I need to store two different models in the database in different collections. These models extends a common that have some similar information. I started deciding in runtime what class it would be used, but right now my code is showing a warning: unchecked call to 'save(T)' as a member of type 'Strategy'.

Below is the code I'm trying to do. For now, I just added a @SuppressWarnings("unchecked") and it's working so far, but I'd like to confirm if this might cause problems and what would be a better approach.

Question: How could I fix this?

Code as of now:

interface Strategy<T extends Person> {
    T save(T model);
    //other methods
}

class StudentStrategy implements Strategy<Student> {
    private StudentRepository studentRepository;

    public Student save(Student student) {
        return studentRepository.save(student);
    }
}
class TeacherStrategy implements Strategy<Teacher> {
    private TeacherRepository teacherRepository;

    public Teacher save(Teacher teacher) {
        return teacherRepository.save(teacher);
    }
}

class PersonService {
    void doSomething(Person person) {
        Strategy strategy = StrategyFactory.getStrategy(person.getType());
        strategy.save(person); //THIS LINE SAYS A unchecked call to 'save(T)' as a member of type 'Strategy'
    }
}

class StrategyFactory {
    public static Strategy getStrategy(PersonType personType) {
        if(personType == STUDENT) return new StudentStrategy();
        if(personType == TEACHER) return new TeacherStrategy();
        return null;
    }
}

Old Code:

This is the code I was doing previously. As you can see, there are a lot of if/else. Changing the repository to store Person is not an options as I need the information of each sub class..

class OldPersonService {
    void doSomething(Person person) {
        if(person.getType == STUDENT) {
            studentRepository.save(person);
        } else {
            teacherRepository.save(person);
        }
        person.setBirthday(new Date());
        person.setName("john");
        if(person.getType == STUDENT) {
            studentRepository.findReferals(person);
        } else {
            teacherRepository.findReferals(person);
        }
    }
}