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

What type of collection does entrySet() return?

1. List

2. Set

3. Queue

4. Map

The correct answer is: Set

The entrySet() method returns a Set because it is designed to return all pairs (key-value) contained in a Map as a Set. Even though a Set is similar to a List in that both can store multiple values, a Set is more suitable since it does not allow duplicates. A Queue on the other hand is used for specific data manipulation such as insertion and deletion at different ends, and thus does not relate to the entrySet() method. Finally, although a Map also stores key-value pairs, it does not return the entire entries as a Set and therefore is not the correct type of collection for the entrySet() method.