15.10.3. Lower Bounded Wildcards

Try these first

1. 1.

   What does the wildcard syntax '<? super T>' allow you to do?

   Hint

   Think about what the 'super' in the wildcard refers to.

2. 2.

   In the context of wildcards, what does PECS stand for?

   Hint

   It's a mnemonic to help remember how to use wildcards.

3. 3.

   What can you add to a List defined as List<? super Integer>?

   • Only Integers
   • Only Objects
   • Integers and its supertypes

   Hint

   Think about what 'super' means in terms of type hierarchies.

4. 4.

   In what scenario is it most beneficial to use lower bounded wildcards?

   Hint

   Consider why you might want more flexibility in what can be added.

5. 5.

   Write a Java method that uses lower bounded wildcards to allow adding elements of different shapes into a list. Describe the potential constraints.

   Hint

   Think about how shapes can be categorized. You can add circles and squares, but reading needs a specific type.

6. 6.

   Imagine a scenario where you need to process different types of vehicles (cars, trucks, etc.). Write a method using lower bounded wildcards to manage these vehicle types.

   Hint

   Consider what happens when you try to read vehicles from the list. Can you guarantee their type?