src/main/java/io/reactivex/processors/PublishProcessor.java
public boolean offer(T t) {
        if (t == null) {
            onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
            return true;
        }
        PublishSubscription<T>[] array = subscribers.get();

        for (PublishSubscription<T> s : array) {
            if (s.isFull()) {
                return false;
            }
        }

        for (PublishSubscription<T> s : array) {
            s.onNext(t);
        }
        return true;
    }
public boolean offer(T t) {
        if (t == null) {
            onError(new NullPointerException("onNext called with null. Null values are generally not allowed in 2.x operators and sources."));
            return true;
        }
        PublishSubscription<T>[] array = subscribers.get();

        for (PublishSubscription<T> s : array) {
            if (s.isFull()) {
                return false;
            }
        }

        for (PublishSubscription<T> s : array) {
            s.onNext(t);
        }
        return true;
    }
Tries to emit the item to all currently subscribed Subscribers if all of them
has requested some value, returns false otherwise.
<p>
This method should be called in a sequential manner just like the onXXX methods
of the PublishProcessor.
<p>
Calling with null will terminate the PublishProcessor and a NullPointerException
is signalled to the Subscribers.
<p>History: 2.0.8 - experimental
@param t the item to emit, not null
@return true if the item was emitted to all Subscribers
@since 2.2