Hi,
I was working on upgrading another library of mine from Java 8 to 11,
and I noticed my unit tests started failing. Some debugging traced the
cause back to java.util.Collections$UnmodifiableMap$UnmodifiableEntrySet
and its iterator() implementation.
In Java 8, the implementation only implemented hasNext, next and remove.
It inherited forEachRemaining from java.util.Iterator, which first does
a null check.
Since Java 11, the forEachRemaining is overridden:
public void forEachRemaining(Consumer<? super Map.Entry<K, V>> action) {
i.forEachRemaining(entryConsumer(action));
}
The thing is, entryConsumer does not perform any null checks. That's
done before entryConsumer is called in all occurrences but this one. The
result is that a non-null action is passed to i.forEachRemaining, which
causes the iterator to move forward before a NullPointerException is
thrown. The solution is of course simple: add
Objects.requireNonNull(action); to the method.
Rob
