15.10. Wildcards in Generics

Try these first

1. 1.

   What does <?> represent in generics?

   Hint

   Think about flexibility in type.

2. 2.

   In the context of wildcards, what does 'extends' signify?

   Hint

   Consider when reading types.

3. 3.

   What wildcard allows any type?

   • <?>
   • <? extends T>
   • <? super T>

   Hint

   Think about 'flexibility'.

4. 4.

   True or False: The syntax <? extends Number> allows reading elements that are of type Number or its subtypes.

   • True
   • False

   Hint

   Think about types of numbers.

5. 5.

   Write a method that accepts a list of any type using an unbounded wildcard and calculates the total number of items added to the list. How would you approach it?

   Hint

   Focus on the size of the list.

6. 6.

   Create a utility function that adds items of type T to a list that accepts upper bounded wildcards. Provide an example of its usage.

   Hint

   Think of the method signature and its parameters carefully.