Today, we’ve come up with a mind-boggling Java collections framework quiz featuring 25 best questions to help you learn the concept of Java collections. The Java collections framework (JCF) is a system of classes and interfaces that implement reusable collection data structures like lists, set hashmaps, etc.
Just for your information, we must tell you that Java collection is the most frequently asked topic in any Java interview so the quiz would help you a lot to get prepared. That’s the reason we’ve ramped up this quiz for both software developers and test engineers so that they can assess their Java programming skills.
Another important aspect to come out with such a quiz was to train our readers on the topic of Java collections. So that they get to know all the important facts about the Java collections. Hence, we’ve tried our best to add all the relevant collections-centric questions in this quiz to make it as meaningful as it could be. Also, we’ve extended the quiz with 25 questions and it’s now a bit more than the usual size of our earlier quizzes. 🙂
Java Collections Quiz with 25 Questions
Answer Key with Reasoning
Here’s the reasoning table explaining each correct answer concisely:
| Q# | Correct Answer | Reasoning |
|---|---|---|
| 1 | ArrayList is not legacy. | ArrayList was introduced in Java 1.2, while Vector is a legacy class. |
| 2 | ArrayList uses dynamic array. | ArrayList dynamically resizes, whereas LinkedList is a doubly linked list. |
| 3 | Iterator moves forward only. | Iterator can only traverse elements forward, unlike ListIterator. |
| 4 | Iterator supports both types. | Iterator allows modification, while Enumeration does not. |
| 5 | List holds duplicates. | List allows duplicate elements, while Set ensures uniqueness. |
| 6 | HashSet is unordered. | HashSet does not maintain order, while TreeSet sorts elements. |
| 7 | Set holds only values. | Set contains only unique values, whereas Map holds key-value pairs. |
| 8 | HashSet has values only. | HashSet contains unique values, whereas HashMap stores key-value pairs. |
| 9 | HashMap is unordered. | HashMap does not maintain key order, while TreeMap sorts by keys. |
| 10 | HashMap is not synchronized. | Hashtable is synchronized, whereas HashMap is not. |
| 11 | Iterator Pattern | The Iterator design pattern is used to traverse collections. |
| 12 | hashCode() | hashCode() determines the bucket where a key-value pair is stored. |
| 13 | Arrays.asList() | Converts an array to a fixed-size List view. |
| 14 | HashMap allows null keys. | HashMap allows one null key, while ConcurrentHashMap does not. |
| 15 | For insert/delete. | LinkedList is better for frequent insertions and deletions. |
| 16 | For index-based access. | ArrayList is faster for index-based access than LinkedList. |
| 17 | Different keys, same hash. | Hash collision occurs when different keys have the same hash code. |
| 18 | It is synchronized. | IdentityHashMap is not synchronized, unlike Hashtable. |
| 19 | No null keys/values. | WeakHashMap allows null keys and values. |
| 20 | Use unmodifiableSet(). | Collections.unmodifiableSet() creates a read-only Set. |
| 21 | Thrown if method missing. | UnsupportedOperationException occurs when an unsupported method is called. |
| 22 | Immutable collection. | Generic collections are type-safe but not necessarily immutable. |
| 23 | 0.75 | The default load factor in HashMap is 0.75 for balancing performance. |
| 24 | Recovers after failure. | Fail-fast iterators throw ConcurrentModificationException and do not recover. |
| 25 | None of these. | All listed classes implement Set. |
Key Takeaways from Java Collections Quiz
Interested software developers and automation test engineers are also welcome to refer to our recently published posts on Java.
1. Java Programming Quiz for Beginners
2. Google Search Using Java and Selenium
3. Java Native Access Tutorial with Example
We hope you would have come here after attempting the quiz. So tell us how well you scored and share your experience. We expect that all software developers and test engineers will have fun trying the quiz and appreciate us for bringing out such a brain teaser.
In the end, we rest assured that we’ll keep coming up with new quizzes on hot topics and will update the earlier ones as well. Being a reader, you too can support us by sharing this post with your friends and on all social media platforms that you like.
All the Best,
TechBeamers
