Collections Questions

Transcription

1 Collections Questions What are Collection related features in Java 8? 2. What is Java Collections Framework? List out some benefits of Collections framework? 3. What is the benefit of Generics in Collections Framework? 4. What are the basic interfaces of Java Collections Framework? 5. Why Collection doesn t extend Cloneable and Serializable interfaces? 6. Why Map interface doesn t extend Collection interface? 7. What is an Iterator? 8. What is difference between Enumeration and Iterator interface? 9. Why there is not method like Iterator.add() to add elements to the collection? 10. Why Iterator don t have a method to get next element directly without moving the cursor? 11. What is different between Iterator and ListIterator? 12. What are different ways to iterate over a list? 13. What do you understand by iterator fail-fast property? 14. What is difference between fail-fast and fail-safe? 15. How to avoid ConcurrentModificationException while iterating a collection? 16. Why there are no concrete implementations of Iterator interface? 17. What is UnsupportedOperationException? 18. How HashMap works in Java? 19. What is the importance of hashcode() and equals() methods? 20. Can we use any class as Map key? 21. What are different Collection views provided by Map interface? 22. What is difference between HashMap and Hashtable? 23. How to decide between HashMap and TreeMap? 24. What are similarities and difference between ArrayList and Vector? 25. What is difference between Array and ArrayList? When will you use Array over ArrayList? 26. What is difference between ArrayList and LinkedList? 27. Which collection classes provide random access of it s elements? 28. What is EnumSet? 29. Which collection classes are thread-safe? 30. What are concurrent Collection Classes? 31. What is BlockingQueue?

2 32. What is Queue and Stack, list their differences? 33. What is Collections Class? 34. What is Comparable and Comparator interface? 35. What is difference between Comparable and Comparator interface? 36. How can we sort a list of Objects? 37. While passing a Collection as argument to a function, how can we make sure the function will not be able to modify it? 38. How can we create a synchronized collection from given collection? 39. What are common algorithms implemented in Collections Framework? 40. What is Big-O notation? Give some examples? 41. What are best practices related to Java Collections Framework? 42. What is Java Priority Queue? 43. Why can t we write code as List<Number> numbers = new ArrayList<Integer>();? 44. Why can t we create generic array? or write code as List<Integer>[] array = new ArrayList<Integer>[10]; Describe the Collections type hierarchy. What are the main interfaces, and what are the differences between them? Describe various implementations of the Map interface and their use case differences. Explain the difference between LinkedList and ArrayList. What is the difference between HashSet and TreeSet? How is HashMap implemented in Java? How does its implementation use hashcode and equals methods of objects? What is the time complexity of putting and getting an element from such structure? What is the purpose of the initial capacity and load factor parameters of a HashMap? What are their default values?

3 Describe special collections for enums. What are the benefits of their implementation compared to regular collections? What is the difference between fail-fast and fail-safe iterators? How can you use Comparable and Comparator interfaces to sort collections? What is the difference between ArrayList and Vector? What is the difference between ArrayList and LinkedList? What is the difference between Iterator and ListIterator? What is the difference between Iterator and Enumeration? What is the difference between List and Set? What is the difference between HashSet and TreeSet? What is the difference between Set and Map? What is the difference between HashSet and HashMap? What is the difference between HashMap and TreeMap? What is the difference between HashMap and Hashtable? What is the difference between Collection and Collections? What is the difference between Comparable and Comparator? What is the advantage of Properties file?

4 What does the hashcode() method? Why we override equals() method? How to synchronize List, Set and Map elements? What is the advantage of the generic collection? What is hash-collision in Hashtable and how it is handled in Java? What is the Dictionary class? What is the default size of load factor in hashing based collection? What is the difference between Array and ArrayList? What is the difference between the length of an Array and size of ArrayList? How to convert ArrayList to Array and Array to ArrayList? How to make Java ArrayList Read-Only? How to remove duplicates from ArrayList? How to reverse ArrayList? How to sort ArrayList in descending order? How to synchronize ArrayList? When to use ArrayList and LinkedList? What is Collection? What is a Collections Framework? What are the benefits of Java Collections Framework? What is the root interface in collection hierarchy?

5 What is the difference between Collection and Collections? Which collection classes are synchronized or thread-safe? Name the core Collection interfaces? What is the difference between List and Set? What is the difference between Map and Set? What are the classes implementing List and Set interface? What is an iterator? What is the difference between Iterator and Enumeration?

6 Which design pattern followed by Iterator? Which methods you need to override to use any object as key in HashMap? What is the difference between Queue and Stack?

7 How to reverse the List in Collections? How to convert the array of strings into the list? What is the difference between ArrayList and Vector? What is the difference between HashMap and Hashtable? What is the difference between peek(),poll() and remove() method of the Queue interface? What is the difference between Iterator and ListIterator. What is the difference between Array and ArrayList in Java? What is the difference between HashSet and TreeSet?

8 Write java code showing insertion,deletion and retrieval of HashMap object? What is the difference between HashMap and ConcurrentHashMap? Arrange the following in the ascending order (performance): HashMap, Hashtable, ConcurrentHashMap and Collections.SynchronizedMap How HashMap works in Java? What is the difference between LinkedList and ArrayList in Java?

9 What are Comparable and Comparator interfaces? List the difference between them? Why Map interface does not extend the Collection interface in Java Collections Framework? When to use ArrayList and when to use LinkedList in application? Write the code for iterating the list in different ways in java?

10 How HashSet works internally in java? What is CopyOnWriteArrayList? How it is different from ArrayList in Java? How HashMap works in Java? How remove(key) method works in HashMap? What is BlockingQueue in Java Collections Framework? How TreeMap works in Java? What is the difference between Fail- fast iterator and Fail-safe iterator? How ConcurrentHashMap works internally in Java?

11 How do you use a custom object as key in Collection classes like HashMap?

12 What is hash-collision in Hashtable? How it was handled in Java?

13 Explain the importance of hashcode() and equals() method? Explain the contract also? What is EnumSet in Java? What are concurrentcollectionclasses? How do you convert a given Collection to SynchronizedCollection? What is IdentityHashMap? What is WeakHashMap? How will you make Collections readonly? What is UnsupportedOperationException? Suppose there is an Employee class. We add Employee class objects to the ArrayList. Mention the steps need to be taken, if I want to sort the objects in ArrayList using the employeeid attribute present in Employee class. What are common algorithms used in the Collections Framework? How to sort ArrayList in descending order? What is the difference between ArrayList and Vector? What is the difference between ArrayList and LinkedList? What is the difference between HashMap and Hashtable? What is the difference between HashSet and TreeSet? What is the difference between ArrayList and HashMap?

14 What is the difference among List, Set and Map interfaces? What is the difference between Iterator and ListIterator? What is the difference between Iterator and Enumeraton? How to synchronize HashMap? How to synchronize ArrayList? What is the difference between fail-fast and fail-safe? How to convert array to ArrayList? How to remove repeated elements from ArrayList?

15 How to loop ArrayList? What is Difference between Hashtable and HashMap in Java? What is the difference between Hashtable and ConcurrentHashMap in Java? What is Difference between Iterator and Enumeration in Java? What is Difference between fail-safe and fail-fast Iterator in Java? How HashMap works internally in Java? Can you write code to traverse Map in Java on 4 ways? What is the difference between Vector and ArrayList in Java? What is the difference between ArrayList and LinkedList in Java? What is the difference between List and Set in Java? How do you find if ArrayList contains duplicates or not?