Java TreeSet MCQ Questions and Answers

1. What is a TreeSet in Java?

a) A dynamic array
b) A type of linked list
c) A collection that uses a tree for storage
d) A hash table implementation

Answer:

c) A collection that uses a tree for storage

Explanation:

TreeSet in Java is a NavigableSet implementation that uses a Red-Black tree for storage.

2. How are elements stored in a TreeSet?

a) In random order
b) In the order of insertion
c) In sorted order
d) In reverse order

Answer:

c) In sorted order

Explanation:

Elements in a TreeSet are stored in a sorted (ascending) order.

3. Can a TreeSet contain duplicate elements?

a) Yes
b) No
c) Only null elements can be duplicated
d) Only numeric elements can be duplicated

Answer:

b) No

Explanation:

TreeSet cannot contain duplicate elements; it only allows unique elements.

4. What must elements of a TreeSet implement?

a) The Set interface
b) The List interface
c) The Comparable or Comparator interface
d) The Serializable interface

Answer:

c) The Comparable or Comparator interface

Explanation:

Elements in a TreeSet must implement the Comparable interface, or you can provide a Comparator at TreeSet creation time for custom sorting.

5. What happens if you try to add a null element to a TreeSet?

a) It's added to the start of the set
b) It's added to the end of the set
c) A NullPointerException is thrown
d) It replaces the smallest element

Answer:

c) A NullPointerException is thrown

Explanation:

Attempting to add a null element to a TreeSet will result in a NullPointerException.

6. How do you remove an element from a TreeSet?

a) remove()
b) delete()
c) discard()
d) clearElement()

Answer:

a) remove()

Explanation:

The remove() method is used to remove a specific element from a TreeSet.

7. How do you access the first element in a TreeSet?

a) first()
b) getFirst()
c) begin()
d) head()

Answer:

a) first()

Explanation:

The first() method returns the first (lowest) element currently in the TreeSet.

8. What is the time complexity of basic operations like add, remove, and search in a TreeSet?

a) O(1)
b) O(log n)
c) O(n)
d) O(n^2)

Answer:

b) O(log n)

Explanation:

Basic operations in a TreeSet, such as add, remove, and search, have a time complexity of O(log n).

9. Can a TreeSet be synchronized?

a) Yes
b) No
c) Only in multi-threaded applications
d) Only if it's empty

Answer:

a) Yes

Explanation:

A TreeSet can be synchronized by using Collections.synchronizedSortedSet().

10. How do you get a reverse order view of the elements in a TreeSet?

a) reverse()
b) descendingSet()
c) invert()
d) reverseOrder()

Answer:

b) descendingSet()

Explanation:

The descendingSet() method returns a reverse order view of the elements contained in the TreeSet.


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