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

Which of these is not a direct subtype of Collection?

1. Set

2. List

3. Queue

4. Map

The correct answer is: Map

All of the options are subtypes of Collection except for D Map. A Set is a subtype of Collection because it allows for multiple unique elements to be stored and does not allow for duplicates. A List is a subtype of Collection because it allows for a sequence of elements to be stored and allows for duplicates. A Queue is a subtype of Collection because it stores elements in a first-in, first-out manner. However, a Map is not a subtype of Collection because it does not store elements in a collection-like manner, but rather stores entries in a key-value pair format.