Unit 2: Object Orientated Programming

Question 1

What are the 3 main characteristics of an object?

Answer 1

State (attributes), Behavior (methods), Identity.

Question 2

What is a class in Java?

Answer 2

A blueprint for creating objects, defining fields and methods.

Question 3

What is the relationship between a class and an object?

Answer 3

An object is an instance of a class.

Question 4

Give two attributes and one method of a Circle class.

Answer 4

Attributes: radius, x; Method: area()

Question 5

What are instance variables?

Answer 5

Fields that store object-specific data.

Question 6

Why are methods used in a class?

Answer 6

To define actions/behaviors that objects can perform.

Question 8

What is a constructor in Java?

Answer 8

A special method to initialize an object, named after the class.

Question 9

How do you instantiate an object in Java?

Answer 9

ClassName obj = new ClassName();

Question 10

What is the role of the new keyword?

Answer 10

Allocates memory and calls the constructor.

Question 11

How do you call a method on an object?

Answer 11

objectName.methodName()

Question 12

What is garbage collection in Java?

Answer 12

Automatic removal of unreferenced objects from memory.

Question 13

What does the private and public keyword do in Java?

Answer 13

• private: It restricts access to a variable or method to within the same class only.
• public: It allows access to a method or variable from any other class.

Question 14

What is encapsulation in Java?

Answer 14

The practice of keeping fields private and accessing them through public methods.

Question 15

Why is encapsulation important?

Answer 15

t hides internal details, protects data, and allows control over how data is accessed or modified.

Question 16

What is a getter method?

Answer 16

A public method that returns the value of a private field.

Question 17

What is a setter method?

Answer 17

A public method that updates the value of a private field.

Question 18

Write a simple getter for a private name field.

Answer 18

public String getName() {
return name;
}

Question 19

What are the benefits of using getters and setters?

Answer 19

They provide controlled access, validation, and flexibility to change implementation.