Unit-1 Questions

I. Introduction to Java

A. Core Concepts (JVM, Platform Independence)

1. What is the Java Virtual Machine (JVM)? Discuss its advantages.

2. What is the difference between the Java Development Kit (JDK) and the JVM?

3. Define "platform independence." What makes Java platform-independent? Explain in detail.

4. Can Java run on any machine? Justify your answer.

B. Class Fundamentals

1. Explain the core concepts of Object-Oriented Programming (OOP) in Java: Encapsulation, Inheritance, and Polymorphism.

2. Explain each word in the standard Java main method signature: public static void main (String args[]).

C. Declaring Objects, Assigning Object Reference Variables

1. What is a class? What is an object? Explain the difference between a class and an object with an example.

2. How do you define a class and create objects from that class in Java? Provide an illustrative example.

3. What are access control modifiers (access specifiers) supported by Java? Explain the different types (e.g., public, private, protected, default/package-private) and illustrate their usage and effect on class members with an example.

D. Introducing Methods, Constructors

1. Define a constructor. Discuss its special properties and advantages.

2. Explain how constructors can be overloaded with the help of an example.

3. Programming Exercise: Create a Swapper class with:

   • Two integer instance variables, x and y.
   • A constructor that takes two integer parameters to initialize x and y.
   • A getX() method that returns the value of x.
   • A getY() method that returns the value of y.
   • A void swap() method that swaps the values of x and y. Then, create a SwapperDemo class to test all the methods of the Swapper class.

4. Programming Exercise: An Employee class contains the following members:

   • Data members: emp_no, emp_name, basic, da, IT, Net_sal.
   • Member functions: To initialize data, to calculate net salary, and to print data members.

   Write a Java program to read the data for an employee and compute their net salary. The DA (Dearness Allowance) is 60% of the basic pay. The IT (Income Tax) is 20% of the basic pay if the basic pay is less than 1,500,000, otherwise, it is 30% of the basic pay. Net_sal = basic + da - IT.

E. The this Keyword, Garbage Collection, The finalize() Method

1. Discuss the use and purpose of the this keyword in Java.

2. What is Garbage Collection in Java?

3. What does the finalize() method do? Explain its role with an example in the context of garbage collection.

F. Exploring the String Class, Using Command-Line Arguments

1. Write a Java program to find the area of a rectangle using command-line arguments to pass the length and width.

G. Varargs, Scanner Class

1. What are variable-length arguments (varargs) in Java? What are the advantages of using them?

2. Illustrate the use of varargs with a programming example.

3. Discuss the usage of the Scanner class in Java for input operations.

II. Inheritance

A. Inheritance Basics

1. What is inheritance in Java?

2. What are the advantages of using inheritance?

3. Provide an example of inheritance in Java.

4. Illustrate inheritance with an example, specifically showing the effect of private and default (package-private) access modifiers on inherited members.

B. Using super, Creating a Multilevel Hierarchy

1. Describe the use of the super keyword in the context of inheritance. Provide an example.

2. Illustrate with an example how to invoke a superclass constructor from its subclass using super().

3. Explain the order of constructor execution in a multilevel hierarchy of classes with an example.

C. When Constructors Are Called, Method Overriding

1. Define method overriding and method overloading. Illustrate both concepts with Java code examples.

2. What are the rules for method overriding in Java?

3. How is dynamic polymorphism (runtime polymorphism) achieved through method overriding? Provide an example.

D. Dynamic Method Dispatch

1. What is Dynamic Method Dispatch in Java?

2. Illustrate Dynamic Method Dispatch (also known as runtime polymorphism) with a programming example.

E. Using Abstract Classes

1. What is an abstract class in Java? Provide an example.

2. Explain the syntax and use of an abstract class.

3. Programming Exercise: Create an abstract class named Shape. Create two subclasses, Rectangle and Triangle, that extend Shape. Include appropriate methods in both subclasses to calculate and return their respective areas.

F. Using final with Inheritance

1. What is the purpose of the final keyword in Java? Explain and provide code examples for its three primary uses:

   • final variables (constants)

   • final methods (cannot be overridden)

   • final classes (cannot be extended)

2. Explain the role and significance of the java.lang.Object class in the Java class hierarchy.