Mastering Java: The Ultimate Quiz for 'Thinking in Java'

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Dive into the depths of Java with our quiz based on "Thinking in Java, Fourth Edition" by Bruce Eckel. Test your knowledge, solidify concepts, and prepare for certification with challenging questions and insightful feedback.

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

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Under what circumstance is it safe to cast an object from a List<? extends Fruit>?

When casting to Fruit or any of its subclasses
Only when casting to an Apple
When you are certain of the list's element types
It is never safe to cast objects from such a list

The correct answer is: When you are certain of the list's element types

When casting an object from a List<? extends Fruit>, the only safe circumstance is when you are completely certain of the list's element types. This means that you know, without a doubt, that all elements in the list are of a specific subtype of the Fruit class. Option A is incorrect because simply casting to Fruit or any of its subclasses is not always safe. Option B is incorrect because relying on the fact that the list can only contain Apples is not a guarantee of safety. Option D is incorrect because there are some situations where it is safe to cast from such a list, as in the case of being certain of the element types.