Java Classes

Question 1

What is object oriented programming?

Answer 1

object-oriented programming is about creating objects that contain both data and methods

Question 2

What are classes in Java?

Answer 2

A Class is like an object constructor, or a “blueprint” for creating objects.

Question 3

What is an object?

Answer 3

An object is an instance of a class. You would instantiate an object which would call the constructor of the object and then depending on the parameters involved you would set the variables and then have access to the methods.

Question 4

What are Java Class Attributes?

Answer 4

Attributes are variables within a class and can be any of the data types

Question 5

How would you access attributes in an object?

Answer 5

You can access attributes by creating an object of the class, and by using the dot syntax (.):

Question 6

How do you modify an attribute?

Answer 6

By using the assignment operator = after the object is created

Question 7

How does the keyword final affect an attribute in a class?

Answer 7

It makes it so you can’t modify the value.

Question 8

How would you call a static method in a class?

Answer 8

Would simply call the method myStaticMethod(); in the main method

Question 9

How would you call a non-static method?

Answer 9

Would need to first create an object and then use the dot notation to access the method.

Question 10

What is a constructor in Java?

Answer 10

A constructor in Java is a special method that is used to initialize objects. The constructor is called when an object of a class is created. It can be used to set initial values for object attributes

Question 11

What are constructor parameters?

Answer 11

Constructors can also take parameters, which is used to initialize attributes. Parameters are data that is passed into the object to set attributes or for method calls.

Question 12

What are the two types of modifiers for methods in Java?

Answer 12

1- Access

2 - Non-access

Question 13

What are the different access modifiers for classes, methods, and attributes?

Answer 13

For classes, you can use either public or default. For attributes, methods and constructors, you can use the one of the following

Question 14

What are the different non-access modifiers for classes, methods, and attributes?

Answer 14

For classes, you can use either final or abstract. For attributes and methods, you can use the one of the following

Question 15

What is a static method?

Answer 15

A static method means that it can be accessed without creating an object of the class, unlike public

Question 16

What is an abstract method?

Answer 16

An abstract method belongs to an abstract class, and it does not have a body. The body is provided by the subclass

Question 17

What is encapsulation?

Answer 17

he meaning of Encapsulation, is to make sure that “sensitive” data is hidden from users. To achieve this, you must:

declare class variables/attributes as private
provide public get and set methods to access and update the value of a private variable

Question 18

What are getter and setter methods in java?

Answer 18

The get method returns the variable value, and the set method sets the value

Question 19

Why is encapsulation important?

Answer 19

Better control of class attributes and methods
Class attributes can be made read-only (if you only use the get method), or write-only (if you only use the set method)
Flexible: the programmer can change one part of the code without affecting other parts
Increased security of data

Question 20

What is a package?

Answer 20

A package in Java is used to group related classes. Think of it as a folder in a file directory. We use packages to avoid name conflicts, and to write a better maintainable code. Packages are divided into two categories:

Built-in Packages (packages from the Java API)
User-defined Packages (create your own packages)

Question 21

What is the this keyword and how is it used?

Answer 21

It is used in the constructor to set the value of the variable in the class and to reference it.

Question 22

What is the super keyword and how is it used?

Answer 22

It is used to call the constructor of the parent class or reference a variable or method of the parent class

Question 23

What is the toString method and how is it created?

Answer 23

it is a method that is called to verify the contents of the variables defined in a class. It can be created automatically with most IDE’s