Java Collections Framework

Question 1

What are the 2 interfaces in the Java Collections Framework?

Answer 1

Map
Collection

Question 2

What is the benefit of collections being generic?

Answer 2

Polymorphism.
Bugs caught at compile time.

Question 3

What are the 4 structures in that inherit Collection?

Answer 3

Set, List, Queue, Dequeue

Question 4

Define each of the 3 set implementations…

Answer 4

HashSet : No order; fastest.
TreeSet : Order based on value; Slower than hash set.
LinkedHashSet : Order based on input.

Question 5

Are List structures ordered?

Answer 5

Yes.

Question 6

What are the 2 concrete implementations of List?

Answer 6

ArrayList
LinkedList

Question 7

Define the Queue structure…

Answer 7

A collection of data stored for processing. FIFO processing.

Question 8

What are the 4 main methods for Queue?

Answer 8

add : Adds element to queue if possible, throws exception if not.
offer : Adds element to queue if possible. Returns false if not.
remote : Removes and returns the head of the queue, throws NoSuchElementException if not.
poll : Remove and returns head of queue, returns null if not.

Question 9

Define a Dequeue…

Answer 9

A double ended queue that can be inserted and deleted from either end.

Question 10

What are the 3 types of operation on Dequeue?

Answer 10

Insert, Remove, Examin.

Question 11

Define the Map interface…

Answer 11

No a direct collection, rather a collection of references that map to values.

Question 12

Define the 3 types of map…

Answer 12

HashMap : Fastest, order irrelevant.
TreeMap : Order guaranteed based on value.
LinkedHashMap : Order based on order of insertion.