MATRUSRI ENGINEERING COLLEGE�DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

SUBJECT NAME: OOP USING JAVA

BE III SEM 2022-23

FACULTY NAME: A V MURALI KRISHNA

MATRUSRI

ENGINEERING COLLEGE

UNIT-1

MATRUSRI

ENGINEERING COLLEGE

Object Oriented Programming: Principles, Benefits Of Object Oriented Programming.

Introduction To Java: Java Buzzwords, Bytecode. Java Programming Fundamentals: Applet And Application Program Using Simple Java Program, Data Types, Variables, Arrays, Operators, Expressions, Control Statements, Type Conversion And Casting, Concepts Of Classes, Objects, Constructors, Methods, Access Control, This Keyword, Garbage Collection, Overloading Methods And Constructors, Introducing

Access Control, Static, Final, Nested And Inner Classes, Exploring String Class, Using Command-linear Arguments.Inheritance: Inheritance Concept, Types Of Inheritance, Member Access Rules, Use Of Super And Final. Polymorphism - Dynamic Binding, Method Overriding, Abstract Classes And Methods.

Syllabus

INTRODUCTION:��

PRELIMINARY CONCEPTS

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OUTCOMES:

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JAVA was developed by Sun Microsystems Inc in 1991, later acquired by Oracle Corporation. It was developed by James Gosling and Patrick Naughton. It is a simple programming language.  Writing, compiling and debugging a program is easy in java.  It helps to create modular programs and reusable code.

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Course Objective: To understand fundamentals of object-oriented programming in Java which includes defining classes, invoking methods, difference between applet and application programs, using class libraries

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Achieve proficiency in object-oriented concepts and also learns to incorporate the same into the Java programming language

CONTENTS:�1) Principles, Benefits Of Object Oriented Programming �2) Java Buzzwords, Bytecode. Java Programming Fundamentals: Applet And Application Program Using Simple Java Program, Data Types, Variables, Arrays, Operators, Expressions, Control Statements, Type Conversion And Casting, Concepts Of Classes, Objects, Constructors, Methods, Access Control, This Keyword, Garbage Collection, Overloading Methods And Constructors .�3) Introducingaccess Control, Static, Final, Nested And Inner Classes, Exploring String Class, Using Command-linear Arguments.Inheritance: Inheritance Concept, Types Of Inheritance, Member Access Rules, Use Of Super And Final. Polymorphism - Dynamic Binding, Method Overriding, Abstract Classes And Methods ��

OUTCOMES:

Achieve proficiency in object-oriented concepts and also learns to incorporate the same into the Java programming language

MODULE-I

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PRINCIPLES OF OBJECT ORIENCTED PROGRAMMING

Encapsulation. Encapsulation is the mechanism of hiding of data implementation by restricting access to public methods.

Abstraction. Abstract means a concept or an Idea which is not associated with any particular instance. Using abstract...

Inheritance. Inheritances expresses is-a and/or has-a relationship between two objects. Using Inheritance, In...

Polymorphism. It means one name many forms. It is further of two types static and dynamic.

Static polymorphism is achieved using method overloading and dynamic polymorphism using method overriding. It is closely related to inheritance. We can write a code that works on the superclass, and it will work with any subclass type as well.

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BENEFITS OF OBJECT ORIENTED PROGRAMMING

• We can build the programs from standard working modules that communicate with one another, rather than having to start writing the code from scratch which leads to saving of development ...
• OOP language allows to break the program into the bit-sized problems that can be solved easily (one object at a time).
• The new technology promises greater programmer productivity, better quality of software and lesser maintenance cost.
• OOP systems can be easily upgraded from small to large systems.

It is possible that multiple instances of objects co-exist without any interference

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JAVA BUZZWORDS

1. Simple
2. Object oriented
3. Distributed
4. Compiled and interpreted
5. Robust
6. secure

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BYTECODE

Java bytecode is the instruction set for the Java Virtual Machine. It acts similar to an assembler which is an alias representation of a C++ code. As soon as a java program is compiled, java bytecode is generated. In more apt terms, java bytecode is the machine code in the form of a .class file. With the help of java bytecode we achieve platform independence in java.

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APPLET AND APPLICATION PROGRAM USING SIMPLE JAVA PROGRAM

Applet is a special type of program that is embedded in the webpage to generate the dynamic content. It runs inside the browser and works at client side.

There are many advantages of applet. They are as follows:

It works at client side so less response time.

Secured

It can be executed by browsers running under many plateforms, including Linux, Windows, Mac Os etc.

DATA TYPES AND VARIABLES

Data types specify the different sizes and values that can be stored in the variable. There are two types of data types in Java:

Primitive data types: The primitive data types include boolean, char, byte, short, int, long, float and double.

Non-primitive data types: The non-primitive data types include Classes Interfaces and Arrays

A variable is a name assigned to a value that is stored inside the system memory

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ARRAYS

• An array is a collection of similar type of elements which has contiguous memory location.
• Java array is an object which contains elements of a similar data type. Additionally, The elements of an array are stored in a contiguous memory location. It is a data structure where we store similar elements. We can store only a fixed set of elements in a Java array.
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• Array in Java is index-based, the first element of the array is stored at the 0th index, 2nd element is stored on 1st index and so on.

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OPERATORS

Operator in Java is a symbol that is used to perform operations

There are many types of operators in Java

Unary Operator,

Arithmetic Operator,

Shift Operator,

Relational Operator,

Bitwise Operator,

Logical Operator,

Ternary Operator and

Assignment Operator.

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EXPRESSIONS

Expressions are constructed from operands and operators. The operators of an expression indicate which operations to apply to the operands. The order of evaluation of operators in an expression is determined by the precedence and associativity of the operators.A Java expression consists of variables, operators, literals, and method calls. To know more about method calls,

For example:

Double a = 2.2, b = 3.4, result;

result = a + b - 3.4;

Here, a + b - 3.4 is an expression.

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CONTROL STATEMENTS

Java provides statements that can be used to control the flow of Java code. Such statements are called control flow statements. It is one of the fundamental features of Java, which provides a smooth flow of program.

Java provides three types of control flow statements.

1.Decision Making statements

if statements

switch statement

2.Loop statements

do while loop

while loop

for loop

for-each loop

3.Jump statements

break statement

continue statement

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TYPE CONVERSION AND CASTING

In Java, type casting is a method or process that converts a data type into another data type in both ways manually and automatically. The automatic conversion is done by the compiler and manual conversion performed by the programmer.

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CONCEPTS OF CLASSES

In object-oriented programming, a class is a basic building block. It can be defined as template that describes the data and behavior associated with the class instantiation. Instantiating is a class is to create an object of that class that can be used to access the member variables and methods of the class.

In general, class declaration includes the following in the order as it appears:

• Modifiers: A class can be public or has default access.
• class keyword: The class keyword is used to create a class.
• Class name: The name must begin with an initial letter (capitalized by convention).
• Superclass (if any): The name of the class's parent (superclass), if any, preceded by the keyword extends. A class can only extend (subclass) one parent.

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ACCESS CONTROL

We can control the access level for class member variables and methods through access specifiers.

Java's access specifiers are public, private, protected and a default access level.

Access Specifier: Access specifier or modifier is the access type of the method. It specifies the visibility of the method. Java provides four types of access specifier:

Public: The method is accessible by all classes when we use public specifier in our application.

Private: When we use a private access specifier, the method is accessible only in the classes in which it is defined.

Protected: When we use protected access specifier, the method is accessible within the same package or subclasses in a different package.

Default: When we do not use any access specifier in the method declaration, Java uses default access specifier by default. It is visible only from the same package only.

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THIS KEYWORD

“this” is a reference variable that refers to the current object.

this can be used to refer current class instance variable.

this can be used to invoke current class method (implicitly)

this() can be used to invoke current class constructor.

this can be passed as an argument in the method call.

this can be passed as argument in the constructor call.

this can be used to return the current class instance from the method.

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GARBAGE COLLECTION

Garbage Collection is process of reclaiming the runtime unused memory automatically. In other words, it is a way to destroy the unused objects.It makes java memory efficient because garbage collector removes the unreferenced objects from heap memory.It is automatically done by the garbage collector(a part of JVM) so we don't need to make extra efforts.

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OVERLOADING METHODS AND CONSTRUCTORS

Overloading allows different methods to have the same name, but different signatures where the signature can differ by the number of input parameters or type of input parameters or both. Overloading is related to compile-time (or static) polymorphism.

// Java program to demonstrate working of method overloading in Java.

public class Sum {

// Overloaded sum(). This sum takes two int parameters

public int sum(int x, int y)

{

return (x + y);

}

// Overloaded sum(). This sum takes three int parameters

public int sum(int x, int y, int z)

{

return (x + y + z);

}

// Overloaded sum(). This sum takes two double parameters

public double sum(double x, double y)

{

return (x + y);

}

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Constructor overloading

The constructor overloading can be defined as the concept of having more than one constructor with different parameters so that every constructor can perform a different task.

Program: Student.java

public class Student {

//instance variables of the class

int id;

String name;

Student(){

System.out.println("this a default constructor");

}

Student(int i, String n){

id = i;

name = n;

}

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STATIC

The static keyword in Java is used for memory management mainly. We can apply static keyword with variables, methods, blocks and nested classes. The static keyword belongs to the class than an instance of the class.

The static can be:

• Variable (also known as a class variable)
• Method (also known as a class method)
• Block
• Nested class

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class Student{  

   int rollno;//instance variable  

   String name;  

   static String college ="ITS";//static variable  

FINAL

The final keyword in java is used to restrict the user. The java final keyword can be used in many context. Final can be:

variable

method

class

The final keyword can be applied with the variables, a final variable that have no value it is called blank final variable or uninitialized final variable. It can be initialized in the constructor only. The blank final variable can be static also which will be initialized in the static block only.

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NESTED AND INNER CLASSES

Writing a class within another is allowed in Java. The class written within is called the nested class, and the class that holds the inner class is called the outer class. Nested classes are divided into two types

• Non-static nested classes (Inner Classes) − These are the non-static members of a class.
• Static nested classes − These are the static members of a class.

STRING CLASS IN JAVA

String is a sequence of characters. In java, objects of String are immutable which means a constant and cannot be changed once created.

There are two ways to create string in Java:

String literal

String s = “matrusri”;

Using new keyword

String s = new String (“matrusri”);

Java String class provides a lot of methods to perform operations on strings such as compare(), concat(), equals(), split(), length(), replace(), compareTo(), intern(), substring() etc.

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COMMAND LINE ARGUMENTS

The java command-line argument is an argument i.e. passed at the time of running the java program.The arguments passed from the console can be received in the java program and it can be used as an input.So, it provides a convenient way to check the behavior of the program for the different values. You can pass N (1,2,3 and so on) numbers of arguments from the command prompt.

Example CommandLineExample.java

class CommandLineExample{  

public static void main(String args[]){  

System.out.println("Your first argument is: "+args[0]);  

}  }  

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1.25

INHERITANCE

On the basis of class, there can be three types of inheritance in java: single, multilevel and hierarchical.In java programming, multiple and hybrid inheritance is supported through interface only.

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1.26

MEMBER ACCESS RULES

Superclass members can be inherited to subclass provided they are eligible by access modifiers. The behavior of access specifiers in the case of inheritance in java is as follows:

1. The private members of the superclass cannot be inherited to the subclass because the private members of superclass are not available to the subclass directly. They are only available in their own class.

2. The default members of the parent class can be inherited to the derived class within the same package.

3. The protected members of a parent class can be inherited to a derived class but the usage of protected members is limited within the package.

4. Public members can be inherited to all subclasses.

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1.27

USE OF SUPER AND FINAL

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SUPER

The super keyword in Java is a reference variable which is used to refer immediate parent class object. Whenever you create the instance of subclass, an instance of parent class is created implicitly which is referred by super reference variable.

Usage of Java super Keyword

• super can be used to refer immediate parent class instance variable.
• super can be used to invoke immediate parent class method.
• super() can be used to invoke immediate parent class constructor.

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1.28

FINAL

The final keyword in java is used to restrict the user. The java final keyword can be used in many context. Final can be:

• variable
• method
• class

The final keyword can be applied with the variables, a final variable that have no value it is called blank final variable or uninitialized final variable. It can be initialized in the constructor only. The blank final variable can be static also which will be initialized in the static block only

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1.29

POLYMORPHISM - DYNAMIC BINDING

“Dynamic” means “run time”, and “binding” means “association”. So the term dynamic binding indicates run time association of objects by java virtual machine.

• Dynamic binding occurs during runtime.
• virtual methods are bonded during runtime based upon runtime object.
• dynamic binding uses object to resolve binding.
• overridden methods are bonded using dynamic binding at runtime.

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1.30

METHOD OVERRIDING

If subclass (child class) has the same method as declared in the parent class, it is known as method overriding in Java. In other words, If a subclass provides the specific implementation of the method that has been declared by one of its parent class, it is known as Method Overriding.

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Java Method Overriding is used for:

• Method overriding is used to provide the specific implementation of a method which is already provided by its superclass.
• Method overriding is used for runtime polymorphism

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Rules for Java Method Overriding

• The method must have the same name as in the parent class
• The method must have the same parameter as in the parent class.

There must be an IS-A relationship (inheritance).

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1.31

ABSTRACT CLASSES AND METHODS

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ABSTRACT CLASS

A class which is declared with the abstract keyword is known as an abstract class in Java. It can have abstract and non-abstract methods (method with the body). It needs to be extended and its method implemented. It cannot be instantiated. It can have constructors and static methods also.

It can have final methods which will force the subclass not to change the body of the method.

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ABSTRACT METHOD

Abstract method can only be used in an abstract class, and it does not have a body. The body is provided by the subclass (inherited from)

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END OF UNIT - I

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