15.10.2 - Upper Bounded Wildcards
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Practice Questions
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What does List<? extends Number> signify?
💡 Hint: Think about what types can be included in the Number class hierarchy.
Why are upper bounded wildcards used?
💡 Hint: Recall how they restrict types to a specific upper limit.
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Interactive Quizzes
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What does <? extends T> mean in Java?
💡 Hint: Think about how generics enforce constraints.
True or False: A List of type List<? extends Animal> can accept a List of Dogs.
💡 Hint: Consider the class hierarchy.
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Challenge Problems
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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.
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.
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