Unit 2- Part 2

Question 1

What does an ADT represent?

Answer 1

the ways of organizing data in a computing environment

Question 2

What does an ADT provide?

Answer 2

provides a specification of:
-a set of data that is stored
-a set of operations that can be performed on the data

Question 3

How are data structures realized?

Answer 3

-by implementing ADTs within a programming language

Question 4

What ADT mean?

Answer 4

Abstract Data Type

Question 5

What is Hashing?

Answer 5

-A technique that determines a storage index or location for storing an item in a data structure

Question 6

What does a hash function do?

Answer 6

-Receives the search key and returns the index of an array where the search key is stored

Question 7

What would a perfect hash function do?

Answer 7

maps each search key into an index of the hash table

Question 8

The Set interface extends what?

Answer 8

extends the Collection interface

Question 9

define Collection

Answer 9

An ADT that contains a group of objects/items

Question 10

define Container

Answer 10

a class that implements the collection

Question 11

List the different types of ADTs

Answer 11

-Bag
-List
-Stack
-Queue
-Dictionary
-Tree
-Graph

Question 12

What is the Bag ADT?

Answer 12

-Unordered collection, may contain duplicates

Question 13

What is the List ADT?

Answer 13

-A collection that numbers (first, second so on) its items

Question 14

What is the Stack ADT?

Answer 14

Orders items sequentially
-Last In, First Out

Question 15

What is the Queue ADT?

Answer 15

-Orders items sequentially
-First In, First Out

Question 16

What is the Dictionary ADT?

Answer 16

Pairs of items (key and value)
-Can be sorted or not

Question 17

What is the Tree ADT?

Answer 17

Arranged in a hierarchy

Question 18

What is the Graph ADT?

Answer 18

Generalization of a tree

Question 19

What are the three types of collections that Java Collections Framework supports?

Answer 19

-Sets
-Lists
-Queue

Question 20

What does the Set interface require?

Answer 20

that an instance of Set contains no duplicate elements
-No two elements e1 and e2 can be in a set such that e1.equals(e2) is true

Question 21

What is the AbstractSet class?

Answer 21

-abstract class that extends AbstractCollection, implements toString() method, and implements Set

Question 22

what does the AbstractSet class provide?

Answer 22

-concrete implementations for the equals() and the hashCode() methods

Question 23

What is the hash code of a set?

Answer 23

the sum of the hash codes of all the elements in the set

Question 24

what is the HashSet class?

Answer 24

a concrete class that implements Set

Question 25

What needs to be to the HashSet class for better efficiency?

Answer 25

-objects added to a hash set need to implement the hashCode() method in a manner that properly disperses the hash code

Question 26

What is the order of the elements inside a HashSet?

Answer 26

There is no specific order of the elements in a hash set -Need to use LinkedHashSet class

Question 27

What is SortedSet and what does it do?

Answer 27

Is a sub-interface of Set -guarantees that the elements in the set are sorted

Question 28

What is a TreeSet?

Answer 28

A concrete class that implements the SortedSet interface

Question 30

How can one add objects into a TreeSet

Answer 30

if they can be compared with each other -Using wrapper classes and classes like String, Date, and Calendar that already implement the Comparable interface -Implementing Comparable or Comparator into your class

Question 31

What is the reason behind using the term "tree" in a TreeSet and TreeMap classes in Java?

Answer 31

They implement the balanced search tree called "red and black tree" -This tree ensures O(logn) lookup which leads to the elements being sorted

Question 32

public int compare(Object element1, Object element2) returns what when the element 1 is less than element2?

Answer 32

A negative value

Question 33

public int compare(Object element1, Object element2) returns what when the element 1 is greater than element2?

Answer 33

A positive value

Question 34

public int compare(Object element1, Object element2) returns what when the element 1 is equal to element2?

Answer 34

Zero

Question 35

What does the List interface allow?

Answer 35

-duplicate elements to be stored in a collection -allows the user to specify where the duplicate element is stored

Question 36

How can the user access the element of a list?

Answer 36

By Index

Question 37

What are the ArrayList and LinkedList classes?

Answer 37

Concrete implementations of the List interface

Question 38

Can a list grow or shrink dynamically?

Answer 38

Yes

Question 39

If the application requires the insertions or deletions of elements at or from any place in the list, which one is better? (LinkedList or ArrayList)

Answer 39

LinkedList

Question 40

What does ArrayList() do?

Answer 40

Creates an empty list with default initial capacity(10)

Question 41

How is the Vector class different from the ArrayList class?

Answer 41

It contains synchronized methods for accessing and modifying the vector

Question 42

How does priority queue order its elements? How does it work?

Answer 42

orders it elements according to the natural ordering using Comparable -the element with the least value is assigned with the highest priority

Question 43

What does PriorityQueue() do?

Answer 43

creates a default priority queue with initial capacity 11

Question 44

In simple terms, what is an iterator?

Answer 44

A program component that steps through a collection of data

Question 45

How can the iterator be manipulated?

Answer 45

-Asked to advanced to the next entry -Give a reference to current entry -Modify the list as it passes through

Question 46

What interfaces does the package java.util in the Java Class Library contain?

Answer 46

-Iterator -ListIterator

Question 47

What are the methods of Iterator interface?

Answer 47

hasNext() next() remove()

Question 48

What has to be called before remove() for there not to be an Exception? What Exception?

Answer 48

next() has to be called before -or you will get IllegalStateException

Question 49

Where is the iterator normally positioned without the next()?

Answer 49

positioned before the first entry or between two entries or after the last entry

Question 50

What does the ListIterator allow?

Answer 50

-traversal in either direction -Modification of list during iteration

Question 51

List the methods that ListIterator contains

Answer 51

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