Question: how can BehavioralRelay value be nullable?

Version: 2.1.0 RxJava: 2.2.6

Since the default value is always there and not null

/**
     * Constructs a BehaviorRelay with the given initial value.
     * @param defaultValue the initial value, not null (verified)
     * @throws NullPointerException if {@code defaultValue} is null
     */
    BehaviorRelay(T defaultValue) {
        this();
        if (defaultValue == null) throw new NullPointerException("defaultValue == null");
        value.lazySet(defaultValue);
    }

and accept(value) doesn’t accept null either

@Override
    public void accept(T value) {
        if (value == null) throw new NullPointerException("value == null");

        setCurrent(value);
        for (BehaviorDisposable<T> bs : subscribers.get()) {
            bs.emitNext(value, index);
        }
    }

How can the value ever be null? 🙏 🤔

/**
     * Returns a single value the Relay currently has or null if no such value exists.
     * <p>The method is thread-safe.
     */
    @Nullable
    public T getValue() {
        return value.get();
    }

I don’t see anywhere value.lazySet or value.set or value = is used in BehavioralRelay.java where it could cause the value to be missing either Hence couldn’t answer my own question

How I use BehavioralRelay

val myRelay :BehavioralRelay<Int> = BehavioralRelay.createDefault(0)
//...
val latestValue = myRelay.value
// do stuffs with the latest value

[JakeWharton]

Like @oldergod said, if you call create() the value will be null until one is supplied so the annotation is correct.

[JakeWharton]

Looks like an accidental holdover from reducing the RxJava BehaviorSubject sources: https://github.com/ReactiveX/RxJava/blob/24df131ecc012aa0591b9123b79a1f0f6a14a4f9/src/main/java/io/reactivex/subjects/BehaviorSubject.java#L320-L327

Feel free to send a PR to change it!