addAll method in List

[yma16]

1 what does ? in addAll(Collection<? extends E> c) mean?
2 what does extends in addAll(Collection<? extends E> c) mean?
(extends seems to mean any data type that is subclass of E)

Thanks a lot

[ra4king]

Have you learned about Generics? I suggest you read about them here:
Lesson: Generics (The Java™ Tutorials > Bonus)

But to answer your questions:
1. ? means any and all classes are acceptable.
2. extends means any and all classes that extend E are acceptable.