PJ_M01_C01_PPT_Introduction to Object Oriented Programming Using Java.pdf

Introduction to
Object Oriented
Programming using
Java
Chapter 1.1

To provide students with the basics of Object
Oriented Programming using Java..
Aim

After completing this chapter, you should be able to:
• Explain the Object Oriented features in Java
• Describe the role of JVM
• Illustrate keywords, variables and data types in Java
• Demonstrate common lexical issues in Java
• Illustrate Java type conversion and casting
• Describe arrays in Java
Instructional Objectives

Learning Outcomes
At the end of this chapter, you are expected to:
• Differentiate between the features of C++ and Java.
• Apply various data types, keywords and variables in a simple Java
program.
• Demonstrate common lexical issues by creating a program in Java to
count the number of spaces, identifiers and comments.
• Describe the types of type conversion with examples.
• Create a program to illustrate the concept of passing an array to method.
• Demonstrate the applications of multidimensional array with an
example.

Introduction to Object Oriented
Programming in Java

I. Object Oriented Programming in Java
Introduction
One of the most important concepts of
programming language is its reliability. Object
Oriented Programming concept helps keeping a
programming language to utmost reliable and
dependable. Let’s look down upon history of Java and
how does it come to existence as a programming
language after C and C++.

Object Oriented Programming in Java
Evolution of Java
Researchers were thinking of a programming language which could be securable,
reusable and support all platforms and also acts as a class-based, object-oriented
with specifically designed dependencies to fix the drawbacks of existing languages
like C and C++. Where C is not secured, and C++ does not have the advanced
characteristic.
It intended to develop an application program which can be "write once and run
anywhere" (WORA), which means the compiled Java code can run on all platforms
that support Java.

History of Java
The most popular programming languages are C, C++, C#, and Java. Where Java is an advanced
programming language and facilitates advanced technical features when compared with each
other.
A revolutionary task to develop a program for digital devices such as set top boxes and television
was an interesting fact which made Java programming to come into existence. It was an advance
concept at that time for Green team members (developers of Java programmers) but it satisfied
the demands of internet programming. Later, Netscape incorporated Java programming.
Java is a propertied language which has its best elements to inherit and combine with any
innovative concept which can build its own unique mission. Java is a technically blended language
which has a rich elements that can address any changing expectations and technical innovations.
At present, Java is one of the most popular programming in use, particularly in client-server
architecture, internet programming, mobile devices, games, e-business solutions etc.

Object Oriented Programming Concepts
Java is an Object Oriented language. It provides the feature to implement an Object
Oriented model, where it is organised around objects and logic rather than data. It
is used in the beginning of software lifecycle and also used to develop other
applications.
Object Oriented Programming is a technique in which programs are written on the
basis of objects e.g. (Java) where it adopts a concept that views everything as an
object and implements a logic in relation to it. Let’s see the concepts of Object
Oriented Programming in detail with an real time example.

Object Oriented Programming
Concepts

Object
An object is nothing but a matter of thing
what we find in everyday life. Technically,
Java is a software bundle of related state and
behaviour.
Example: Car, box, mountain, computer etc.

Object and its components

Object with Its Attributes

Class
In Java programming, class is defined as
a blueprint from which objects are
created. It models and describes the
state and behaviour of an object.
Example: Consider a car with several
properties like clutch, steering, break,
etc.

Inheritance
Inheritance is a property by which state and
behaviour of one class (super class) can be
inherited to its sub-class. It is a powerful
and a natural mechanism for organising and
structuring a software.
Example: Human heredity

Abstraction
Hiding the implementation details from the user is called as abstraction. Here,
only the functionality will be provided. In Java, abstraction can be achieved by
abstract class, and Interface.
A class with an abstract keyword is called as abstraction.
Interface – blueprint of a class. Full abstraction can be achieved using this
mechanism.
Example: Invention of flight is based on the flying mechanism learnt from
birds. So flights are derived form base class birds.

Encapsulation
Encapsulation is one of the fundamental concept of OOP.
Mechanism of binding the data and function together in a single
unit is called as encapsulation.

Polymorphism
Polymorphism is an ability of an object to take many forms. It reacts
differently in different situation. In Java, polymorphism is used to reduce
code complexities. Methods or function of a class implies the behaviour of
polymorphism. In Java, all Java objects are polymorphic.

Components of Java
Java Compiler
Compiler is used to systemize the program and check against language syntax
rules. It converts the source code to byte code and then compiles them. The Java
compiler generates an architecture-neutral object file format (the compiled code –
source code and byte code) to be executable on many processors.
Source code - collection of computer instructions written in human readable format.
Writes the output in java file
Byte code - computer object code, also called as instruction set of Java Virtual Machine.
Writes the output in class file

Java Virtual Machine (JVM)
Java Virtual Machine – enables the computer to run Java program. It reads and interprets
class files and executes the program’s instruction into native hardware platform.
JVM is platform independent (obtainable for many hardware and software platforms). In
the Java virtual machine specification, the behaviour of a virtual machine instance is
described in terms of subsystems, memory areas, data types, and instructions. These
components describe an abstract inner architecture for the abstract Java virtual machine.
The purpose of these components is not so much to dictate an inner architecture for
implementations. It is more to provide a way to strictly define the external behaviour of
implementations. The specification defines the required behaviour of any Java virtual
machine implementation in terms of these abstract components and their interactions.

Let’s discuss what does JVM performs?
 It is used to load the code
 It Verifies and executes the code
 And it provides run time environment

Components of JVM:
Following are the components of JVM:
• Stack
• Heap
• Constant Pool
• Code segment
• Program counter

Components Of JVM
1. Stack
Temporary values are stored in frames of a
stack.
It contains the state of Java method invocation.
While invoking a method, JVM pushes a new
frame onto that thread’s Java stack.
After completion of a single method, the virtual
machine pops and discards the frame for that
method.

Components Of JVM
Heap
Heap consists of objects. The JVM has a
heap that is the runtime data area from which
memory for all class instances and arrays are
allocated.
It is created at the JVM start-up.
• Heap Memory – store Java objects
• Non-heap memory – Store Meta data and
other loaded classes.

Components Of JVM
Constant Pool
Constant pool consist of all constant data.
They comprise of
• Numbers
• Strings
• Symbolic names of classes, interfaces
and fields

Components Of JVM
Program Counter
Tracking of current instruction execution at any
moment is done by Program Counter (PC) register.
It is similar to that of pointer which keeps in track of
current instruction in sequence.
Every time a new thread is created, a PC register is
also created simultaneously.
PC keeps a pointer to the current statement that is
being executed in its thread.

29
Simple Java Program
• Java is a general-purpose programming language. Like any programming
language, Java also has its own syntax, structure and programming paradigm to
build a robust, reusable and maintainable applications programs.
• Java programs are executed in its development environment such as Java
Development Kit (JDK) and Eclipse IDE.
• Programmatically, Java is a derivative of C++language. Syntax of Java looks similar
like C. Code blocks are modularised into methods and delimited by braces ({ })
and variables are declared before they are used.
• Java program starts with a package where the package can be defined as a
namespace mechanism. It helps to maintain the hierarchical file system, manage
file system and class system.

Hierarchy of Java Program Components

Java Program
Example : A simple java program is illustrated below :
public class FirstProgram
{
Public static void main (string [ ]args)
{
Sytem.out.println(“ First Java Program”);
} //end of main
} //end of First Program class

Self – Assessment Questions
1) Java is an architectural dependent programming language.
a) True b) False
2) ______________ is an instance of class.
a) Package b) Object
c) Class d) None of these
3) By default, all Java Objects are Polymorphic.
a) True b) False

Data types, Keywords and Variables

II. Data Types, Keyword and Variables
Variables are memory locations to store values.
When a user creates a variable, a memory space is reserved for that the variable.
Based on the type of the variable, the operating system allocates memory and
decides what can be stored in that reserved space.
A user can store integers, decimals, character, etc. by assigning different data
types to the variables.
Datatype is a keyword used to allocate sufficient memory space for the data.
Pictorial representation of datatypes and its classifications are given below:

Classification of Data types
Let’s see the list of datatypes and its description in the following. The types
are:
• Integer
• Floating point
• Character
• Boolean
• Type conversion and Casting
• Automatic Type promotion in expression

Integers
Java defines four integer types:
Byte short
int long
All of these are signed, positive and negative values.
Java does not support unsigned datatypes. Whereas
signed and unsigned integers are supported by many
other computer languages.
Java designers felt that unsigned integers are
unnecessary because they are mostly used to specify
behavior of the higher order bit, which defines the
sign of an integer value. The width of an integer type
should not be thought of as the amount of storage it
consumes, but rather as the behavior it defines for
variables and expressions of that type. The Java run-
time environment is free to use whatever size it wants,
as long as the types behave as you declared them.

Integers
Integers and its types
Name Width Range
Long
64 -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
Int
32 -2,147,483,648 to 2,147,483,647
Short
16 -32,768 to 32,768
Byte
8 -128 to 127

Bytes
• The smallest integer type is byte.
• This is a signed 8-bit type that has a range from -128 to 127.
• Variables of type byte are especially useful when you’re working with a
stream of data from a network or file.
It can be represented as:
Byte b, c;

Short
• Short is a signed 16-bit type.
• It has a range from –32,768 to 32,767.
• It is probably the least-used Java type.
Here are some examples of short variable declarations:
short s;
short t;

Int
• The most commonly used integer type is int.
• It is a signed 32-bit type that has a range from –2,147,483,648 to
2,147,483,647.
• In addition to other uses, variables of type int are commonly employed to
control loops and to index arrays.

Long
• Long is a signed 64-bit type and is useful for those occasions where an int
type is not large enough to hold the desired value.
• The range of a long is quite large. This makes it useful when big, whole
numbers are needed.

Floating – Point
• Floating-point numbers, also known as real numbers
• There are two kinds of floating-point types :
 Float
 Double
which represent single- and double-precision numbers, respectively.

Floating – Point types
Their Width and ranges are shown below :
Name Width Approximate Range
double 64 4.9e-324 to 1.8e+308
float 32 1.4e-0.45 to 3.4e+0.38

Float
• Float is specified as a single-precision value that uses 32 bits of storage.
• Single precision is faster and takes half as much space as double precision, , but
will become imprecise when the values are either very large or very small.
Here are some example float variable declarations:
float hightemp, lowtemp;

Double
• Double is denoted by the keyword ‘double’ which is used to store a value of 64 bit. It is
faster than single precision on modern processor that have been optimized for high-
speed mathematical calculations. Some importance of double are:
• All transcendental math functions, such as
 sin( )
 cos( )
 sqrt( )
• return double values.
• Double is best choice, when you need to maintain accuracy over many iterative
calculations, or are manipulating large-valued numbers.

Integer
Public class DataType_int
{
int a=100;
int b=-150;
void add( )
{
Int c=a + b;
Sysytem.out.println (“The int
value is:” +c);
}
}
Class Demo
{
public static void main(String
args[ ] )
{
Datatype_Int obj =new
DataType_Int ( );
Obj.add();
}
}
Output:
The int value is -50

Double Integer
// Compute the area of a circle.
class Area {
public static void main(String args[])
{double pi, r, a;
r = 10.8; // radius of circle
pi = 3.1416; // pi, approximately
a = pi * r * r; // compute area
System.out.println("Area of circle is " + a);
}
}
Output:
Area of circle is 366.435

Characters
• char in Java is not the same as char in C or C++.
• Java uses Unicode to represent characters.
• Unicode defines a fully international character set that can represent all of the
characters found in all human languages.
• It is a unification of dozens of character sets, such as
 Latin
 Greek
 Arabic
 Cyrillic
 Hebrew

Characters
• In Java, char is 16 bit and ranges from 0 to 65,536.
• There are no negative chars.
• The standard set of characters known as ASCII still ranges from 0 to 127 as
always, and the extended 8-bit character set, ISO-Latin-1, ranges from 0 to 255.

Characters
Example Program : Demonstrates char variables
class CharDemo {
public static void main(String args[]) {
char ch1, ch2;
ch1 = 88; // code for X
ch2 = 'Y';
System.out.print("ch1 and ch2: ");
System.out.println(ch1 + " " + ch2);
}
}
This program displays the following output:
ch1 and ch2: X Y

Boolean
The Boolean logical operators are:
| , & , ^ , ! , || , && , == , != .
• Java supplies a primitive data type called Boolean, instances of which can take
the value true or false only, and have the default value false.
• The major use of Boolean facilities is to implement the expressions which
control if decisions and while loops.

Boolean
Example program:
class Boolean
{
public static void main(String args[])
{
// these are boolean variables
boolean A = true;
boolean B = false;
System.out.println ("A|B = "+(A|B));
System.out.println ("A&B = "+(A&B)); // program execution using boolean
System.out.println ("!A = "+(!A));
System.out.println ("A^B = "+(A^B));
System.out.println ("(A|B)&A = "+((A|B)&A));
}
}
Syntax:
booleanValue(); // returns the value of Boolean object

Type conversion and Casting
• Type casting is used to assign value of one type of a variable to another type.
Casting in other words is an instruction to the compiler to convert one type to
another.
• It helps Java not only to perform only arithmetic operations on pairs of values of
same type but performs operations on mixed type too.
• For example the value of the right side is automatically converted to the type of
the left side in compatible types.
• In Java, Boolean and int are not compatible.
• When the above said conditions are met, a widening conversion takes place.

Types : There are two types
Types Casting
Widening casting Narrowing Casting

1) Widening casting
In widening casting, the value types are not directly expressed. Here, integer and
floating are compatible with each other. Integer literal can be assigned to char.
Widening
Byte Short Int Long Float Double

2) Narrow casting:
In narrow casting, the value types are directly expressed.
Narrowing
Double Float Long Int Short Byte

Difference between Widening and Narrowing
Widening Casting Narrowing Casting
Used to access new methods of child class or
while referring super class to child class
Used to access redefined class of parent class in the child class

Sample Program:
Package conversion;
Public class main
{
Public Static Void main(string [ ] args)
{
int var1=12;
double var2=15.2;
double result = var1+var2;
System.Out.Println (“The sum is” + result)
}
}

1) Boolean is used to control the decisional statement in a program
a) True b) False
2) Java supplies a primitive data type called_________________.
a) Integer b) Float
c) Boolean d) Character
3) Any size of an integer is handled by Java.
a) True b) False

Lexical Issues
• Java programs are the collection of whitespace, identifiers, literals, comments
and separators.
• Lexical issues are very common in programming, which is used to analysis,
operate and implement the program in a sequential order.

Lexical Issues
Let us see the detail description of lexical issues in the following.
i. Whitespace
• As word by itself, a whitespace is nothing but a space, tab, or a new line.
• Java is a case sensitive free-form language which means a user need not follow
any special rules.
• For example, there is no format to be followed to write a Java program.
• A program can be written even in a single line or any number of lines can be
used, whatever user wishes.
• By default, single whitespace is required between each character.

Lexical Issues
Identifiers
• An identifier can be described as any descriptive sequence of uppercase,
lowercase letters, underscore or a dollar -sign character.
• Identifiers are used for specifying class name, method name and variable name.
Since Java is case-sensitive language any letter of a word will be different from the
other form of the similar word.
• Let us say in Java, a word max is different from MAX.

Lexical Issues
Literals
Literals are used to specify a default value or to declare a constant value.
It can be a:
• Boolean – True or False
• Numeric – floating, decimal, integer or a fixed point
• Character based – single character or a string

Lexical Issues
Comments
Three types of comments are supported by Java. They are
Comment Description
/*text*/ Compiler ignores everything from /* to */
//text Compiler ignores everything from // to the end
of the line
//**documentation*/ Called as doc comment (documentation
comment) – used by automatically generated
document

Lexical Issues
Separators
Separators are characters used to terminate statements. Commonly used separators
are semicolon (;). Following are few separators used in Java programs
Symbol Name Purpose
( ) Parenthesis Control the order of operation
{ } Braces Used to group statements and
declaration
[ ] Brackets Used to declare array types and
dereferencing array values
; semicolon Terminates statement
, comma Separates consecutive identifiers in a
variable decalaration

1) ____________line space is required to separate each statement.
a) Single b) Double
c) More than one d) Not required
2) Java is a case-sensitive programming language.
a) True b) False
3) _______ is used to store values specified by a data type.
a) Variables b) Identifiers
c) Literals d) Separators

Arrays
Array is a collection of similar types of elements that have contiguous memory location.
It is a container object that holds values of homogeneous type. Java array is container object that
contains elements of similar data type.
It can have : Only fixed set of elements which can be stored in it.
Also have label as static data structure because during the time of declaration only the size of the
array is specified. An array containing number of variables and it can even start from zero – which is
called as an empty, instead they are referenced by array access expressions that use non-negative
integer index values.
Syntax:
datatype[ ] identifier; Or datatype identifier;

Arrays
Initialization of an array:
[ ] - Int operator is used to initialize an array.
Example program:
Int [] arr = new int [15]; // 15 is the size of an array

Array
Array Type :
Array types are used in declarations and in cast expression. An array type is written as the name of
an element type followed by some number of empty pairs of square brackets []. The number of
bracket pairs indicates the depth of array nesting.
An array's length is not part of its type. It may be of any type, whether primitive or reference.
• Arrays with an interface type as the element type are allowed. An element of such an array
may have as its value a null reference or an instance of any type that implements the interface.
• An array with an abstract class type as the element type are allowed. An element of such an
array may have as its value a null reference or an instance of any subclass of the abstract class
that is not itself abstract.

Array
Array Variable:
A variable of an array type enfolds a reference to an object. It is used to create a
variable and does not create any space to that specified variable. Some of the
variable declarations are listed below. They are:
Declaration Comment
Int [ ] Array of int
Short [ ] [ ] Array of short
Object [ ] Array of object
Collection<?> Array of collection of unknown types

Array
Single Dimensional Array:
A one-dimensional array consist of a list of like-typed variables.
The general form of a one-dimensional array declaration is
The general form of new as it applies to one- dimensional arrays, appears as
follows:
arrayRefVar =new dataType[arraySize];
type var-name[ ]; // syntax

Array
The above statement does two things:
1. It creates an array using new dataType[arraySize];
2. It assigns the reference of the newly created array to the variable arrayRefVar.
The example below allocates a 12-element array of integers and links them to
month_days.
month_days = new int[12];
After this statement executes, month_days will refer to an array of 12 integers.
Further, all elements in the array will be initialized to zero.

Array
You can access a specific element in the array, once after you allocate an array by
Specifying its index within square brackets. All array indexes start at zero.
For example, this statement assigns the value 28 to the second element of
month_days.
month_days[1] = 28;
The next line displays the value stored at index 3.
System.out.println(month_days[3]);

Array
Putting together all the pieces, here is a program that creates an array of the
number of days in each month.
// Demonstrate a one-dimensional
array.
class Array {
public static void main(String
args[]) {
int month_days[];
month_days = new int[12];
month_days [0] = 31;
System.out.println ("April has " +
month_days[3] + " days.");
}
}

Array
When you run this program, it prints the number of days in April. As mentioned,
Java array indexes start with zero, so the number of days in April is
month_days[3] or 30.
It is possible to combine the declaration of the array variable with the allocation
of the array itself, as shown here:

Array
Multidimensional Array
Java does not support multidimensional arrays. However, you can declare and
create an array of arrays
However, as you will see, there are a couple of subtle differences. To declare a
multidimensional array variable, specify each additional index using another set of
square brackets. For example, the following declares a two dimensional array
variable called twoD.
int twoD [ ] [ ] = new int[4][5];

// Demonstrate a two-dimensional array.
class TwoDArray {
public static void main(String args[]) {
int twoD[ ] [ ]= new int[4][5];
int i, j, k = 0;
for(i=0; i<4; i++)
for(j=0; j<5; j++) {
twoD[i][j] = k;
k++;
}
for(i=0; i<4; i++) {
for(j=0; j<5; j++)
System.out.print(twoD[i][j] + " ");
System.out.println();
}}}
This program generates the
following output:
0 1 2 3 4
5 6 7 8 9
10 11 12 13 14
15 16 17 18 19
The following program numbers each element in the array from left to right, top to
bottom, and then displays these values:

Summary
 Java is an Object Oriented Programming Language.
 Java is a technically blended language which has a rich elements that can address any changing
expectations.
 Java adopts a concept that views very thing as an object and places an extra ordinary demands
on the programs.
 Variables are memory locations to store values.
 A class is defined as blueprint from which objects are created.
 Casting is an instruction to the compiler to convert one type to another.
 Separators are characters used to terminate statements.
 Array is a collection of similar types of elements that have contiguous memory location.
 Java does not support multi-dimensional array

Subjective Questions
1. Explain various data types, keywords and variables with an
example Java program
2. What is an array in Java? Explain its types with an example.
3. What are lexical issues and explain how does it help in
program implementation?

• Brief description of activity
Activity
• Do an online study and prepare a presentation of
10-15 slides which describes the evolution of Java
from C++.
• You are required to:
• Differentiate between C++ and Java and list down
the secure features of Java when compared to C++.
• Pen down the strategies used in Java to make it
reliable and robust with a real time example.
Online Activity
(30 min)

• The complete reference Java-2: Herbert Schildt-5th edition- McGraw
Hill professional
• SAMS teach yourself Java-2- Rogers Cedenhead and Leura Lemay- 3rd
edition – Pearson
e-References

PJ_M01_C01_PPT_Introduction to Object Oriented Programming Using Java.pdf

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