Java Collections Framework

Review your understanding of Lists,Sets,Maps,and their implementations.

1. Which interface in the Java Collections Framework allows duplicate elements and maintains insertion order?
2. Which class is a resizable array implementation of the List interface?
3. HashSet does not allow duplicate elements.
4. Which of the following are implementations of the Set interface?
5. What is the root interface of the Java Collections Framework (excluding Map interfaces)?
6. Which collection does NOT allow null elements?
7. LinkedList provides faster insertion at the middle compared to ArrayList.
8. Which of the following collections are sorted by default?
9. What is the initial capacity of an ArrayList when created with the default constructor?
10. HashMap is synchronized (thread-safe) by default.
11. What method is used to add an element to the end of a List?
12. Which of the following statements about ArrayList and LinkedList are true?
13. Which Map implementation maintains entries in insertion order?
14. The List interface provides a method to retrieve an element by index.
15. What is the interface that represents a collection of key-value pairs?
16. Which of the following methods are part of the Collection interface?
17. Which interface represents an ordered collection that does not allow duplicate elements?
18. Vector is a legacy class and is thread-safe.
19. What method is used to obtain an iterator over a Collection?
20. Which of the following are immutable collections?
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