CODEWITHSUNDEEP
javajava-8functional-programmingjava-streamoption-type
user12051965
user12051965

Reputation: 147

Check if null attribute present in Optional and return String Java Stream API

I have the following 

class Person
  private String firstName;
  private String familyName;

  // Setters and Getters

And I have the following method

public String getFullName(Optional<Person> persons) {
  return persons
           .map(person -> (person.getFirstName() + " " + person.getFamilyName())).orElse("Invalid");
}

I just want to check if either first or last name is null, display "Invalid" for that person. I was thinking to add a method for validation but I am sure there is an easier way I cannot think about.

Upvotes: 1

Views: 1597

Answers (3)

ETO
ETO

Reputation: 7279

Another functional approach.

First create a predicate builder method for required field validation:

public static <T, F> Predicate<T> hasRequiredValue(Function<T, F> fieldGetter) {
    return fieldGetter.andThen(Objects::nonNull)::apply;
}

And modify the getFullName a little bit:

public Optional<String> getFullName(Person person) {
    return Optional.ofNullable(person)
                   .filter(hasRequiredValue(Person::getFamilyName))
                   .filter(hasRequiredValue(Person::getFirstName))
                   .map(p -> p.getFirstName() + " " + p.getFamilyName());
}

Then use it as follows:

Person person = ...
String fullName = getFullName(person).orElse("Invalid");

Upvotes: 1

Youcef LAIDANI
Youcef LAIDANI

Reputation: 59988

You are looking to Optional::filter, before the map:

return persons
        .filter(person -> person.getFamilyName() != null && person.getFirstName() != null)
        .map(person -> person.getFirstName() + " " + person.getFamilyName())
        .orElse("Invalid");

Which mean, if the family and first names are not null then create your concatination, otherwise return an Invalid message, or you can even throw an exception by using orElseThrow

Upvotes: 4

Andronicus
Andronicus

Reputation: 26046

You can use filter for that:

public String getFullName(Optional<Person> persons) {
  return persons
           .filter(person -> Objects.nonNull(person.getFirstName()) && Objects.nonNull(person.getFamilyName()))
           .map(person -> (person.getFirstName() + " " + person.getFamilyName())).orElse("Invalid");
}

Upvotes: 1

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