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Practice Questions
Test your understanding with targeted questions related to the topic.
Question 1
Easy
What does List<? extends Number> signify?
💡 Hint: Think about what types can be included in the Number class hierarchy.
Question 2
Easy
Why are upper bounded wildcards used?
💡 Hint: Recall how they restrict types to a specific upper limit.
Practice 4 more questions and get performance evaluation
Interactive Quizzes
Engage in quick quizzes to reinforce what you've learned and check your comprehension.
Question 1
What does <? extends T> mean in Java?
- Allows writing to any object of type T.
- Allows reading any object of type T or its subclasses.
- Blocks the use of any subclass of T.
💡 Hint: Think about how generics enforce constraints.
Question 2
True or False: A List of type List<? extends Animal> can accept a List of Dogs.
- True
- False
💡 Hint: Consider the class hierarchy.
Solve and get performance evaluation
Challenge Problems
Push your limits with challenges.
Question 1
Implement a generic method that calculates the sum of a list containing any number subclasses. Ensure type safety through upper bounded wildcards.
💡 Hint: Student should focus on using `doubleValue()` on the Number class.
Question 2
Create a class that manages a collection of objects from various subclasses of a parent class, ensuring it utilizes upper bounded wildcards when retrieving items.
💡 Hint: Pay attention to the class definition and method parameter signatures.
Challenge and get performance evaluation