QuipoIn

Java HashSet

Which of the following is true about HashSet?

A. It allows duplicate elements 

B. It maintains insertion order 

C. It allows one null element 

D. It is synchronized by default

Which data structure does HashSet use internally?

A. Array 

B. Linked List 

C. HashMap 

D. TreeMap

What is the time complexity of add() and contains() in HashSet (average case)?

A. O(1) 

B. O(n) 

C. O(log n) 

D. O(n²)

What happens if you add a duplicate element in HashSet?

A. It throws an exception 

B. It overwrites the old element 

C. It ignores the duplicate 

D. It adds duplicate at the end

Which of the following is not true about HashSet?

A. HashSet allows duplicate elements 

B. HashSet is unordered 

C. HashSet allows one null value 

D. HashSet uses hashing