Final Exam

Question 1

Definition of a class…

Answer 1

A class is the template/blueprint from which individual objects are created; it describes the behaviors/states that object of its type support.

Collection of data members and methods

Question 2

Definition of an object…

Answer 2

Objects have states and behaviors; they are an instance of a class.

Question 3

Example of an object.

Answer 3

Dog:
states - color, name, breed
behaviors - wagging, barking, eating

Question 4

Definition of a method…

Answer 4

Collection of statements that are grouped together to perform an operation.

Question 5

What is a modifier…

Answer 5

Defines the access type of the method and it is optional to use.

Question 6

What is the purpose of a constructor?

Answer 6

Initializes an object when it is created; create an instance of a class!

Can take only access modifiers – cannot be abstract, final, native, static, or synchronized.

Do not have a return type.

Have same name as their class name.

Uppercase.

Usually a noun.

Question 7

When do you use a constructor?

Answer 7

To give initial values to the instance variables defined by the class, or to perform any other startup procedures required to create a fully formed object.

Question 8

Does Java have a default constructor?

Answer 8

Java automatically provides a default constructor that initializes all member variables to zero.

Question 9

What is an instance member?

Answer 9

Memory space is created each and every time whenever an object is created.

Meant for storing specific values.

Question 10

What is a static member?

Answer 10

Memory space is created only once – when the class is loaded in the main memory; no objects are created.

Meant for storing common values.

Question 11

What are the two types of data members?

Answer 11

Static

Instance (aka. non-static)

Question 12

How is an instance data member accessed?

Answer 12

Object name.

Question 13

How is a static data member accessed?

Answer 13

Class name.

Question 14

What is the purpose of a method?

Answer 14

To execute code.

Question 15

Give an example of a constructor for the class: Platypus

Answer 15

Platypus p1 = new Platypus();

Question 16

Describe what a super class does…

Answer 16

Calls the overridden method of the superclass.

Question 17

What class does Java extend when you do not explicitly extend a class?

Answer 17

Object class.

Question 18

Why would we want to overload a constructor?

Answer 18

When we need more than one constructor which does different-2 tasks.

If you do not want to specify the initial capacity and capacity increment then you can simply use default constructor; example, Vector v = new Vector();

If you need to specify the capacity and increment then you call the parameterized constructor; example, Vector v = new Vector(10, 5);

Question 19

What is used for calling the default constructor from parameterized constructor?

Answer 19

this();

Should always be the first statement in the constructor body.

Question 20

What does a constructor allow you to do?

Answer 20

Create objects from a class.

Question 21

What is a primitive data type?

Answer 21

Predefined by the language and named by a keyword.

8 primitive types in Java: byte, short, int, long, float, double, boolean, char

Question 22

What is a reference data type?

Answer 22

Created using defined constructors of the classes. They are used to access objects. These variables are declared to be of a specific type that cannot be changed; example: Animal animal = new Animal(“giraffe”);

Question 23

Where are instance variables declared?

Answer 23

In a class, but outside a method, constructor or any block.

Question 24

When are instance variables created?

Answer 24

When an object is created with the use of the keyword ‘new’ and destroyed when the object is destroyed.

Question 25

What is the purpose of an instance variable?

Answer 25

Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object’s state that must be present throughout the class.

Instance variables can be declared in class level before or after use.

Question 26

What’s a string?

Answer 26

Sequence of characters.

Question 27

What does it mean when a class implements an interface?

Answer 27

The class inherits all the abstract methods of the interface.

Implicitly abstract and cannot have implementations.

Analogy: Class as signing a contract, agreeing to perform the specific behaviors of the interface.

Question 28

How is an interface declared?

Answer 28

Implements keyword.

Interfaces can extend other interfaces.

public interface NameOfInterface {
   //Any number of final, static fields
   //Any number of abstract method declarations\
}

Question 29

Describe each member of:

public static void main(String [] args)

Answer 29

public - modifier
static - can call method directly using class name and not creating an object of it
void - return type
main - method name
String[] args - string array of type args

Question 30

What is the purpose of the main method in Java?

Answer 30

Provides a start of application execution.

Question 31

What is a BST?

Answer 31

Ordered binary tree.

An abstract data structure where each node has a comparable key.

Smaller keys to the left of the parent.
Larger keys to the right of the parent.
Equivalent keys to the left or right – must keep consistency.

Question 32

Name the three types of BST removal types…

Answer 32

Key with no children.
Key with one child.
Key with two children.

Question 33

Explain the process to remove node with no children…

Answer 33

Remove the node.

Question 34

Explain the process to remove a node with one child…

Answer 34

Promote the child node to the node’s position that was removed.

Question 35

Explain the process to remove a node with two children…

Answer 35

Promote the right most node from the left subtree; largest value that is still less than the one you are replacing; the immediate predecessor in a sequence of values.

Question 36

What is a binary tree?

Answer 36

Tree where each node has up to two leaves.

Question 37

What is an adjacency list?

Answer 37

Collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a vertex in the graph.

Question 38

What is an adjacency matrix?

Answer 38

Square matrix used to represent a finite graph. The elements of the matrix indicate whether pairs of vertices are adjacent or not in the graph.

Question 39

What does it mean to extend a class? How do you extend a class?

Answer 39

Extend by using the extends keyword.

Inheritance allows one class to “inherit” the properties of another class.

If you inherit from class A, then class B will also contain the same fields and methods.

Question 40

What is the syntax for an enhanced for loop?

Answer 40

for(declaration : expression) { }

declaration - of same type; value at each iteration
expression - the array you you need to iterate through

Question 41

What are the three access types and describe their scope…

Answer 41

Visible to the class only (private).

Visible to the world (public).

Visible to the package and all subclasses (protected).

Question 42

Provide an example of a user defined type…

Answer 42

If you have a class named Box; you can create an object of Box, or a user defined data type of Box.

Box b = new Box(); // Object
Box b = nb // User defined

Question 43

What is an AVL tree?

Answer 43

A self-balancing BST; the height of a node’s two child subtrees must not have a difference greater than one.

Searching for a value is faster than in a BST.

Question 44

What is an abstract class?

Answer 44

A Java abstract class can have instance methods that implements a default behavior.

Method that is declared, but contains no implementation