CODEWITHSUNDEEP
javalombok
Thomas
Thomas

Reputation: 1143

NonNull List Items with Lombok

I'm currently building a Java application and using Lombok annotations to reduce boilerplate. I'm running into problems, however, when using the @Singular and @NonNull annotations together. For example, let's look at the following example class:

@Builder
class Classroom {

    @Singular @NonNull
    private List<String> students;
}

I would like the @NonNull annotation to protect from adding null elements singularly, like so:

Classroom.builder()
    .student("Sally")
    .student("Joe")
    .student(null)
    .build();

However, even with the annotation, the null element is still added to the list when the Classroom object is built. Is there an easy way, using Lombok annotations, to mark singular elements as NonNull, or am I going to need to drop the annotations and implement that type of protection myself?

Upvotes: 3

Views: 2882

Answers (1)

Ortomala Lokni
Ortomala Lokni

Reputation: 62683

According to the Lombock documentation :

You can use @NonNull on the parameter of a method or constructor to have lombok generate a null-check statement for you.

So you have to put the @NonNull annotation on the parameter of the student method (in the builder class) and not on the private field students (in the Classroom class).

public student(@NonNull String name){
    students.add(name);
}

Upvotes: 1

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