CODEWITHSUNDEEP
javalambdajava-8nullpointerexceptionnullable
rayman
rayman

Reputation: 21606

Filtering avoiding unexpected null using lambda's inline

I have list for each element I would like to do this (using Java 8):

disabledUsersOnLDAP.stream().forEach(user -> usersRepository
                .findEnabledByUsername(user.getUserName()).setEnabled(false));

How ever usersRepository.findEnabledByUsername might return null.

Of course I can do this instead:

disabledUsersOnLDAP.stream().forEach(user -> {
    UserEntity userEntity = usersRepository.findEnabledByUsername(user.getUserName()); 
    {
        if (userEntity != null) {
            userEntity.setEnabled(false);
        }
    }
});

But I wonder if I could do the null check inline (in the first option)?

Upvotes: 19

Views: 51396

Answers (2)

assylias
assylias

Reputation: 328639

You could do a mapping + filtering before running the forEach part, which also makes it a bit more readable:

disabledUsersOnLDAP.stream()
            .map(user -> usersRepository.findEnabledByUsername(user.getUserName()))
            .filter(userEntity -> userEntity != null)
            .forEach(userEntity -> userEntity.setEnabled(false));

Or as an alternative:

disabledUsersOnLDAP.stream()
            .map(User::getUsername)
            .map(usersRepository::findEnabledByUsername)
            .filter(Objects::nonNull)
            .forEach(userEntity -> userEntity.setEnabled(false));

Upvotes: 47

gontard
gontard

Reputation: 29520

Some alternatives to the @assylias answser.

Use a method reference to Objects==nonNull for the null check:

disabledUsersOnLDAP.stream()
    .map(User::getUsername)
    .map(usersRepository::findEnabledByUsername)
    .filter(Objects::nonNull)
    .forEach(userEntity -> userEntity.setEnabled(false));

if you can update UserEntity with a disable method 

class UserEntity {
    public void disable() {
        setEnabled(false);
    }
}

you can again use a method reference (UserEntity::disable) :

disabledUsersOnLDAP.stream()
    .map(User::getUsername)
    .map(usersRepository::findEnabledByUsername)
    .filter(Objects::nonNull)
    .forEach(UserEntity::disable);

Some resources:

Upvotes: 7

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