Practice Upper Bounded Wildcards (15.10.2) - Collections and Generics - Advanced Programming

Practice: Upper Bounded Wildcards

Lesson 15.10.2Collections and Generics

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8 questions

Flashcard drill
2 cards from this section. Quick, good the night before a test.
Exercise
6 questions · about 4 min · pass mark 70%. Hints available.
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Quiz
2 questions · about 1 min · pass mark 70%. Hints available.
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6 sample questions

Question 1.
What does List<? extends Number> signify?
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Think about what types can be included in the Number class hierarchy.
Question 2.
Why are upper bounded wildcards used?
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Recall how they restrict types to a specific upper limit.
3Question 3.
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.
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Think about how generics enforce constraints.
4Question 4.
True or False: A List of type List<? extends Animal> can accept a List of Dogs.
- True
- False
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Consider the class hierarchy.
Question 5.
Implement a generic method that calculates the sum of a list containing any number subclasses. Ensure type safety through upper bounded wildcards.
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Student should focus on using `doubleValue()` on the Number class.
Question 6.
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.
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Pay attention to the class definition and method parameter signatures.

4 more questions in this section. Enroll free to practise them all.