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!

Practice this question and more.

What restriction does a List<? extends Fruit> impose?

You cannot add any object to the List
You can only add Fruit objects to the List
You can add any subtype of Fruit to the List
No restrictions, any object can be added to the List

The correct answer is: You cannot add any object to the List

A List<? extends Fruit> imposes the restriction that only objects of type Fruit or its subtypes can be added to the list. Option B and C suggest that only objects of type Fruit can be added to the list, but this is incorrect as subtypes of Fruit are also allowed. Option D states that there are no restrictions, but this is incorrect as the list can only contain objects of type Fruit or its subtypes. Option A is the correct answer as it accurately states that no objects can be added to the list, regardless of whether they are of type Fruit or its subtypes. This is because when using the wildcard ? extends Fruit, the compiler cannot determine the specific type of objects that can be added to the list, so it prevents any objects from being added to avoid potential type errors.