Quiz for List, Set, Map, Queue

Q1: Which interface allows duplicate elements in Java?

A. Set B. List C. Map D. Queue

Q2: Which implementation of List is synchronized?

A. ArrayList B. LinkedList C. Vector D. CopyOnWriteArrayList

Q3: Which collection does not allow duplicate keys?

A. HashMap B. ArrayList C. LinkedList D. TreeSet

Q4: Which Set implementation maintains insertion order?

A. HashSet B. TreeSet C. LinkedHashSet D. None of the above

Q5: Which Map implementation is sorted by keys?

A. HashMap B. LinkedHashMap C. TreeMap D. HashTable

Q6: Which queue follows FIFO order?

A. PriorityQueue B. LinkedList (as Queue) C. Deque D. ArrayDeque

Q7: Which class implements both List and Deque interfaces?

A. ArrayList B. LinkedList C. TreeMap D. HashSet

Q8: Which is thread-safe?

A. HashSet B. HashMap C. Vector D. ArrayList

Q9: Which collection does not maintain any order?

A. HashSet B. LinkedHashSet C. TreeSet D. List

Q10: What does the Map interface map?

A. Only keys B. Only values C. Keys to values D. Index to element