Computer Science Final

Question 1

What are the four pillars of OOP?

Answer 1

1) Abstraction
2) Encapsulation
3) Inheritance
4) Polymorphism

Question 2

Define Abstraction

Answer 2

The process of identifying relevant classes, including their data members/values and methods, to solve a problem.

Question 3

Define Encapsulation

Answer 3

Effective information hiding

Question 4

Define Inheritance

Answer 4

Organization of relevant classes into a hierarchy of super-classes and sub-classes such that the sub-classes can inherit the data members and methods of the super class.

Question 5

Define Polymorphism

Answer 5

Execution of different implementations of the exact same method call.

Question 6

What are the benefits of polymorphism?

Answer 6

Smooth and easy extension and modification of a program

Question 7

What are the benefits of inheritance?

Answer 7

• Code Reuse
• Code Maintenance
• Extensibility
• Polymorphism

Question 8

Can an abstract class be instantiated?

Answer 8

No

Question 9

Does a sub-class have to implement the abstract methods of the parent class?

Answer 9

Yes

Question 10

Does a sub-class have to implement all of the methods in an abstract class?

Answer 10

No

Question 11

Create an abstract method called “mystery” that returns a String and can only be used by a sub-class.

Answer 11

protected abstract String mystery( );

Question 12

What are the benefits of an abstract class?

Answer 12

An abstract class is a prototype class that allows the programmer control the base functionality a sub-class must have.

Question 13

What are the benefits of an abstract method?

Answer 13

They allow the programmer to ensure that every sub-class will implement that method.

Question 14

How is an interface different than an abstract class?

Answer 14

An interface only has constants and abstract methods

Question 15

What are the access levels if the “private” specifier is used?

Answer 15

Class

Question 16

What are the access levels if no specifier is used?

Answer 16

Class and Package

Question 17

What are the access levels if the “protected” specifier is used?

Answer 17

Class, Package, and Subclass

Question 18

What are the access levels if the “public” specifier is used?

Answer 18

Class, Package, Subclass, World

Question 19

What is the difference between overloading and overriding a method?

Answer 19

Overloading a method is when different instances of a method expect different parameters.

Overriding a method is when a subclass has the same method name as the parent class, but with a different implementation.

Question 20

When should we use an abstract class as opposed to one that is instantiable?

Answer 20

An abstract class should be used if the sub-classes cover all possible forms of the superclass

Question 21

Is the constructor method of a super-class inherited by its subclass?

Answer 21

No

Question 22

What are the four components of recursion?

Answer 22

1) Stopping Condition
2) End Case
3) Recursive Step
4) Integration Step

Question 23

What is a class?

Answer 23

A class is a template for how objects are created/deployed

Question 24

What does a class have?

Answer 24

A class has both characteristics (data members) and behavior (methods).

Question 25

What is an object?

Answer 25

An object is an instance of a class

Question 26

What are the stages of the software development cycle?

Answer 26

Analysis

Design

Coding

Testing

Operation

Maintenance

Question 27

Draw and explain the event-driven programming diagram

Answer 27

In java there are numerous event sources, including JButton, JTextField, JCheckBox, etc. When the user interacts with these event sources, they fire off events. In order for these events to affect anything, we must attach event listeners to the event sources. Java then automatically attaches event handlers to the event listeners through the use of interface classes. Thus, when an event source fires off an event, the attached event listener will be triggered, which will call the event handler.

Question 28

What are the main purposes of exception handling?

Answer 28

• Improves the reliability (robustness) of our programs
• Provides useful information to client programmers (notifies them if they misuse our program)

Question 29

What are the two types of exceptions?

Answer 29

• Checked
• Unchecked

Question 30

What are the three basic search methods?

Answer 30

• Bubble Sort
• Insertion Sort
• Selection Sort

Question 31

What is the difference between checked and unchecked exceptions?

Answer 31

Checked exceptions are checked at compilation and must be caught or propagated, while unchecked exceptions are not checked at compilation and do not need to be caught.

Question 32

Describe the heapsort algrorithm

Answer 32

1) Construction Phase
- Create a heap (binary tree)
- Make sure the heap meets two constraints:
1) Structural Constraint: Heap is orgranized in a top-down, left-to-right fashion
2) Value-Relationship Constraint: Heap is organized so that the value of each parent node is greater than its children’s values
- Start with the bottom-most, right-most parent node - Make sure its value is greater than that of its children
- If its value is not greater, swap it with the child node that has the greater value and propagate it down. - Repeat for each parent node, moving in a leftward / upward motion
2) Extraction Phase
1) Extraction Step
- Extract the largest value (top-most node) and put it in the output area
2) Reconstruction Step
- Replace the top-most node with the bottom-most, right-most node.
- Reevaluate the necessary parts of the heap
- Compare the top-most node with its children. If it is smaller than its children, swap it with the larger child.
- Keep comparing the node with its children until it is no longer smaller than its children or no longer has children.

Repeat the extraction step until there are no more nodes remaining in the heap

Question 33

What are the benefits of an interface class?

Answer 33

Allows for flexibility and customization

Allows Java to provide services for us

Question 34

What is the difference between a sentinel-controlled loop and a count-controlled loop?

Answer 34

A sentinel-controlled loop continues as long as the given condition is true.

A count-controlled loop continues for a certain number of iterations.

Question 35

Show how to solve the Towers of Hanoi

Answer 35

/* Meaning of variables:

from : pole from which to move disc

to : pole disc is being moved to

spare : pole not involved in disc transfer

n : number of discs on pole/disc number

*/

public long counter = 0;

public void play(int n, int from, int to, int spare) {

       if (n == 1)  {   

                moveOne( from, to );

      } else {    

                play( n-1, from, spare, to);

                moveOne( from, to);

                play( n-1, spare, to, from);

       }

}

private void moveOne (int from, int to) {

      System.out.println( from + " --\> " + to );

       counter++;

}

public static void main(String[] args) {

      TOH game1 = new TOH();

      game1.play(4, 1, 3, 2);

      System.out.println(game1.counter);

}

Question 36

What is the difference between side-by-side problem decomposition and outside-to-inside decomposition?

Answer 36

Side-by-side: Different modules applied to different sub-problems

Outside-to-inside: Same module applied to smaller and smaller sub-problems

Question 37

Explain Merge Sort

Answer 37

Divide the unsorted list into 2 sub-lists recursively until each sub-list contains one element

Then, merge sub-lists to produce new sorted sub-lists until there is only one list remaining

Question 38

Explain Quick Sort

Answer 38

• Select a pivot (first of the list)
• Create 2 sub-lists
  - All #’s less than the pivot in list 1
  - All #’s greater than the pivot in list 2
• Call quick sort on list 1 and list 2
• Concatenate the result of quicksort(list1), the pivot, and quicksort(list2)

Question 39

State the complexity of the basic sort methods, advanced sort methods, basic search method, and binary search method

Answer 39

Basic Sort: O(n^2)

Advanced Sort: O(nlogn)

Basic Search: O(n)

Binary Search: O(logn)

Question 40

Are all public methods of a parent class inherited by a subclass?

Answer 40

No (Constructor)