Avoid IFs

1.java

PersonDAO personDAO = new PersonDAO();
Person person = personDAO.getPersonByID(1);
if(person != null) {
    person.setName("My name");
}

2.java

personDAO.getPersonByID(personID, new Action<Person>() {
    public void act(Person person) {
        person.setName("My name");
    }
});

Action.java

public interface Action<T> {
    void act(T object);
}

Caller.java

public void call() throws PersonNotFoundException {
    PersonDAO personDAO = new PersonDAO();
    Person person = personDAO.getPersonByID(1);
    person.setName("My name");
}

find.java

public String findCarInsurance(Person person) {
    if (person != null) {
        Car car = person.getCar();
        if (car != null) {
            Insurance insurance = car.getInsurance();
            if (insurance != null) {
                return insurance.getName();
            }
        }
    }
    return "Unkonwn";
}

find2.java

public String findCarInsurance(Person person) {
    if (person == null) {
        return "Unkonwn";
    }
    Car car = person.getCar();
    if (car == null) {
        return "Unkonwn";
    }
    Insurance insurance = car.getInsurance();
    if (insurance == null) {
        return "Unkonwn";
    }
    return insurance.getName();

}

find3.java

public String findCarInsurance(Optional<Person> person) {
    return person.flatMap(person1 -> person1.getCar())
            .flatMap(car -> car.getInsurance())
            .map(insurance -> insurance.getName())
            .orElse("Unkonwn");
}

lambda.java

List<Person> persons = personDAO.getPersonByID(1);
persons.forEach(person -> {
    person.setName("My name");
});

person.rb

person_dao.person(id) do |person|
      person.name = name
end

PersonDAO.java

public class PersonDAO {
    
    public Person getPersonByID(int personID) throws PersonNotFoundException {
        Person person = null;
        ...
        ...
        if(person == null) {
            throw new PersonNotFoundException();
        }
        return person ;
    }

}