Quiz Week 3

What is the primary difference between an ArrayList and a HashSet in Java?

• ArrayList is ordered, HashSet is unordered.

• ArrayList allows duplicates, HashSet does not.

• ArrayList is faster for searching, HashSet is faster for insertion.

• All of the above.

Which Java Collection would you use to store a list of unique student IDs?

• ArrayList

• LinkedList

• HashSet

• HashMap

How do you insert an element at a specific index in an ArrayList?

• list.add(index, element)

• list.insert(index, element)

• list.put(index, element)

• list.set(index, element)

What is the time complexity of accessing an element at a given index in an ArrayList?

• O(1)

• O(log n)

• O(n)

• O(n^2)

How does HashSet ensure uniqueness of elements?

• By using a linked list internally.

• By using a hash function to map elements to buckets.

• By sorting the elements.

• By comparing elements using the equals() method.

What is the time complexity of searching for an element in a HashSet?

• a) O(1) on average

• O(log n)

• O(n)

• O(n^2)

Describe a scenario where an ArrayList would be a more suitable choice than a HashSet.

• Storing a list of unique usernames.

• Storing a list of students in the order they enrolled.

• Storing a list of distinct prime numbers.

• Storing a list of unique email addresses.

How would you remove all duplicate elements from an ArrayList?

• Convert the ArrayList to a HashSet and then back to an ArrayList.

• Sort the ArrayList and then remove consecutive duplicates.

• Use a nested loop to compare each element with all other elements.

• There is no direct way to remove duplicates from an ArrayList.

What is the difference between iterator() and listIterator() in ArrayList?

• listIterator() provides bidirectional traversal.

• iterator() can only be used for removal.

• listIterator() can only be used for insertion.

• There is no significant difference between them.

Explain the concept of generics in the context of Java Collections.

• Generics allow you to define the type of objects that can be stored in a Collection.

• Generics improve code readability and prevent type-related errors.

• Generics allow you to create collections of primitive data types.

• All of the above.