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Objects and Collections - Programming

Q1:

Which statement is true for the class java.util.HashSet?

A The elements in the collection are ordered.

B The collection is guaranteed to be immutable.

C The elements in the collection are guaranteed to be unique.

D The elements in the collection are accessed using a unique key.

ANS:C - The elements in the collection are guaranteed to be unique.

Option C is correct. HashSet implements the Set interface and the Set interface specifies collection that contains no duplicate elements. Option A is wrong. HashSet makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. Option B is wrong. The set can be modified. Option D is wrong. This is a Set and not a Map.