Wildcard in generics

Wildcard:

In generics ‘?’ is known as wildcard and it represents an unknown type.

Types of wildcard:

1. 1. Unbounded wildcard.
2. 2. Bounded wildcard.
   1. a. Upper bounded wildcard.
   2. b. Lower bounded wildcard.

1. Unbounded wildcard.is used for list of unknown types using ‘?’(Type is not bounded).
2. Bounded wildcard: is used for unknown bounded types using ‘?’ with extends or super keyword.

1. a. Upper bounded wildcard. is used to restrict the unknown type to be a specific type or a subtype of that type using ‘?’ with extends keyword.
2. b. Lower bounded wildcard. is used to restrict the unknown type to be a specific type or a super type of that type using ‘?’ with super keyword.