8/2/2019 Bt0074 Unit 5 Faqs

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Frequently Asked Questions

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Subject Name: OOPS with Java Subject Code: BT0074

Unit 5: Inheritance, Package and InterfaceBalasubramani R

Assistant ProfessorDept. of IT

Q1: What is Inheritance?

A1: Inheritance is one of the cornerstones of object-oriented programming because it allows

the creation of hierarchical classifications. Using inheritance, you can create a general

class that defines traits common to a set of related items. This class can then be inherited

by other, more specific classes, each adding those things that are unique to it.

Q2: What is a Superclass and Subclass?

A2: In the terminology of Java, a class that is inherited is called a Superclass. The class that

does the inheriting is called a Subclass. Therefore, a subclass is a special version of a

superclass. It inherits all of the instance variables and methods defined by the superclass

and add its own, unique elements.

Q3: What do you mean by Access Specifiers?

A3: An access specifier determines which features of a class (the class itself, the data

members, and the methods) may be used by other classes. Java supports three access

specifiers.

public   – public class members are accessible from anywhere within the program.

private   – only objects of the same class can access a private variable or method.

protected   – the variables, methods, and inner classes that are declared protected are

accessible to the subclasses of the class in which they are declared.

Q4: What is a Package in Java?

A4: Java provides a mechanism for partitioning the class name space into more manageable

chunks. This mechanism is the package. The package is both a naming and a visibility

control mechanism. You can define classes inside a package that are not accessible by

code outside that package. You can also define class members that are only exposed to

other members of the same package. This allows your classes to have intimate

knowledge of each other, but not expose that knowledge to the rest of the world.

Q5: What is an Interface in Java?A5: Using Interface, you can specify what a class must do, but not how it does it. Using the

keyword interface, you can fully abstract a class’ interface from its implementation.

Interfaces are syntactically similar to classes, but they lack instance variables, and their

methods are declared without any body.