Question

In Java, the Collections class contains the following method:

public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> c)

Its signature is well-known for its advanced use of generics,
so much that it is mentioned in the Java in a Nutshell book
and in the official Sun Generics Tutorial.

However, I could not find a convincing answer to the following question:

Why is the formal parameter of type Collection<? extends T>, rather
than Collection<T>? What’s the added benefit?

Answer 1

One benefit of the ? is that it prohibits additions of items to the Collection