This document provides an introduction to the Java programming language. It discusses that Java is an object-oriented programming language used to write computer programs. It also describes the basic elements of the Java language including commands, variables, data types, control statements, and functions/methods. Additionally, it explains that the basic building block of Java is the class, and that a Java program or application consists of multiple classes organized into packages.

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JAVA BASICS
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Java is a Programming Language
A programing language.
Write computer programs
Other programming language:
o C/ C++
o Python
o .Net
o PHP etc.

3. What is programming?
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Video
Game

4. Calculator / Bill Payment
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Basic elements of the Language
1. Command: an action
2. Variables/Attributes: memory to remember data
3. Data Type: number, decimal, character
4. Control Statement: conditional action
5. Functions/Methods: a task contains set of commands

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Java is OOP
3 Idiot
Java is Object Oriented Programming .
follows OOP methodology.
Java thinks only Objects.
 Just like a Money Oriented Person
who always thinks of Money.
मेरी 4 लाख
की घडी!!
मेरी डेढ़ लाख
की शेरवानी!!
My 300$
shoes

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Basic Unit of Java is Object
Program of
1. Print Hello World is an object
2. Sum of two numbers is an object
3. Fibonacci Series is an object
4. SMS Service is an object
5. Email Service is an object
6. Account Service is an object
Basic unit of Java is an Object.
OOP is real world programming.

8. Class: structure of an object
 What object will do? What are responsibilities of an object?
What tasks are done by Object?
 Class is the structure of an Object
 Class defines Role and Responsibilities of an object
 Ultimately a Program is a Class
 When memory is allocated to class, it will become object
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9. Object Vs Class
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State/Variables
• currentGear
• speed
• color
Methods
• changeGear()
• accelerator()
• break()
State
• name
• address
Methods
• changeName()
• earnMoney()
Structure
Real world entities

10. Object Vs Class
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State/Variables
• balance
• owner
• type
Methods
• getBalance()
• fundTransfer ()
• payBill()
Real world entities

11. Class is the basic building block
 The basic building block of Java is a Class.
 Java program is nothing but a Class.
 Java application is made of Classes.
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Class
Class contains program elements
Class contains methods and variables.
Variables contain data
Types of data are int, float, boolean, char
and String.
Methods perform operations.

13. Executable Class
A Class is program
A Class can be executed
Executable Class must contain one method, names
‘main’
When you execute a class main() method is executed
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HelloWorld – First Java Program
1. public class HelloWorld {
2. public static void main(String[] args) {
3. System.out.println(“Hello World”);
4. }
5. }
public, class, static, and void are keywords.
Keywords are always written in small letters.

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Pizza
1. public class Pizza {
2. public static void main(String[] args) {
3. int money = 99;
4. if (money > 100) {
5. System.out.println("Wow!!, I can buy Pizza :)");
6. } else {
7. System.out.println("Oh!, I can not buy Pizza (:");
8. }
9. }
10. }

16. Sum of Two Numbers
public class Sum {
 public static void main(String[] args) {
 int a = 10;
 int b = 5;
 int c = a + b;
 System.out.println(c);
 }
}
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17. Expert Class
Each class is an Expert class
An expert class contains related attributes and methods
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Doctor Advocate Engineer Astronaut

18. Specialization -Inheritance
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Doctor
Heart Specialist ENT Specialist Cancer Specialist

19. Expert never overlaps other’s responsibilities
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Creator Preserver Destroyer
Trimurti

20. Expert Classes
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:Automobile
-color :String
-speed:int
-make:String
+$NO_OF_GEARS
+getColor():String
+setColor()
+getMake():String
+setMake()
+break()
+changeGear()
+accelerator()
+getSpeed():int
:Person
-name:String
-dob : Date
-address:String
+$AVG_AGE
+getName():String
+setName()
+getAdress():String
+setAddress()
+getDob (): Date
+setDob ()
+getAge() : int
:Account
-number:String
-accountType : String
-balance:double
+getNumber():String
+setNumber()
+getAccountType():String
+setAccountType()
+deposit ()
+withdrawal ()
+getBalance():double
+fundTransfer()
+payBill()

21. Experts bring Modularity and Reusability
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Class
Program Structure - Java
int i = 5 //global variable
void main(){
..
a(5);
}
void a(int k){
int j = 0; //local variable
..
}

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Package – group of related classes
Package
Class 1 Class 2
Class 3 Class 4

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JAVA Application
Application
Package 1 Package 2
Package 3 Package 4
 An application has multiple packages

25. Java Platform
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JDK
JRE
Development Kit
javac.exe
JVM
(java.exe)
JAVA Class Libraries
AWT, I/O, Net etc.

26. Compile and Execute
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Hello.java
(text)
JVM (java.exe)
Hello.class
(bytecode)
Compile (javac)
• Compile .java file
• c:>javac Hello.java
• It will generate file Hello.class
• Run the class by
• c:>java Hello

27. Compile once run anywhere
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JVM
Linux
Hello.class
(bytecode)
JVM
MacOS
JVM
Windows

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Control Statements
if-else
while
for
do-while
GOTO
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While Loop
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While Loop
 public class HelloWhile {
 public static void main(String[] args) {
o boolean जबतकहेजान = true;
o int round = 0;
o while (जबतकहेजान ) {
 System.out.println(“मै बसंती नाचंगी !!!");
 if(++round > 500 )
• जबतकहेजान = false;
o }
 }
 }
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For Loop
₹10 for 5 shots
How Much?
Okay!!
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32.  public class HelloFor {
 public static void main(String[] args)
 {
o for (int shot=1; shot <= 5; shot++)
o {
o System.out.println(“Shot Balloon” + i);
o }
o }
 }
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For Loop – Five shots
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Print Hello Java 5 times - for
public class HelloFor {
public static void main(String[] args) {
o for (int i = 0; i < 5; i++) {
 System.out.println("Hello Java ");
o }
o }
}

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Print Hello Java 5 times - while
public class HelloWhile {
public static void main(String[] args) {
o int i = 0;
o while (i < 5) {
 System.out.println("Hello Java ");
 i++; // i = i+1
o }
}
}

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Print Hello Java 5 times – do-while
public class HelloDoWhile {
public static void main(String[] args) {
int i = 0;
o do {
 System.out.println( i+ " Hello Java ");
 i++;
o } while (i < 5);
}
}

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Foreach statement
public class HelloFor {
public static void main(String[] args) {
o int[] table={ 2, 4, 6, 8, 10};
o for (int v : table) {
 System.out.println(“Table “ + v);
o }
o }
}

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Add.java
public class Add {
public static void main(String[] args) {
o int a = 5;
o int b = 10;
o int sum = a + b;
o System.out.println("Sum is " + sum);
}
}

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Java Primitive Data Types
Primitive Data Types:
o boolean true or false
o char unicode (16 bits)
o byte signed 8 bit integer
o short signed 16 bit integer
o int signed 32 bit integer
o long signed 64 bit integer
o float,double IEEE 754 floating point

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java.lang.String class
 String name = "Vijay Dinanath Chauhan";
 S.o.p(" String Length- " + name.length());
 S.o.p(" 7th character is- " + name.charAt(6));
 S.o.p(" Dina index is- " + name.indexOf("Dina"));
 S.o.p(" First i Position- " + name.indexOf("i"));
 S.o.p(" Last i Position- " + name.lastIndexOf("i"));
 S.o.p(" a is replaced by b- " + name.replace("a", "b"));
 S.o.p(“ Chhota vijay- " + name.toLowerCase());
 S.o.p(" Bada vijay- " + name.toUpperCase());
 S.o.p(" Starts With Vijay- " + name.startsWith("Vijay"));
 S.o.p(" Ends with han- " + name.endsWith("han"));
 S.o.p(" Substring- " + name.substring(6));
 Note : S.o.p = System.out.println

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Java.lang.StringBuffer class
 public static void main(String[] args) {
 StringBuffer sb = new StringBuffer("Vijay");
 sb.append(“ Dinanath Chauhan");
 S.o.p("Length : " + sb.length());
 S.o.p("Capacity :" + sb.capacity());
 S.o.p("Char at :" + sb.charAt(1));
 S.o.p("Index Of : " + sb.indexOf("Dinanth"));
 S.o.p("Replace : " + sb.replace(0, 5, "Jay "));
 S.o.p("Reverse : " + sb.reverse());

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String vs StringBuffer
String is immutable
o Memory object can not be changed.
StringBuffer is mutable
o Memory object can be changed.

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java.lang.Math class
 public static void main(String[] args) {
o S.o.p(“ Mathematics functions");
o S.o.p(" Max 2,5 - " + Math.max(2,5));
o S.o.p(" Min 2,5 - " + Math.min(2,5));
o S.o.p(" Absolute 3.7 - " + Math.abs(3.7));
o S.o.p(" Exp 10 - " + Math.exp(10));
o S.o.p(" Random Number- " + Math.random());
o S.o.p(" Square Root- " + Math.sqrt(4));
 }
 Note : S.o.p = System.out.println

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Static vs Instance
String name = “Vijay”;
String surname = “Chauhan”
S.o.p(name.length());
S.o.p(surname.length());
String.length()
S.o.p(Math.max(2,5));
S.o.p(Math.max(5,10));

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Other Data Types
Reference types (composite)
o objects
o arrays
strings are supported by a built-in class named String
(java.lang.String).
string literals are supported by JAVA as a special case.

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Hello <Name>
 public class HelloName {
o public static void main(String[] args) {
o System.out.println("Hello " + args[0]);
o }
 }
 C:>java HelloName Vijay Dinanath Chauhan
 class args[0] args[1] args[2]
 C:>java HelloName “Vijay Dinanath” Chauhan

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Hello Name – if <condition>
 public class HelloName1 {
 public static void main(String[] args) {
o if (args.length == 1) {
 System.out.println("Hello " + args[0]);
o } else {
 System.out.println(“Parameter name is required");
o }
 }
 }

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Hello All
public class HelloAll {
public static void main(String[] args) {
o for (int i = 0; i < args.length; i++) {
 System.out.println(i + " = Hello " + args[i]);
o }
}
}

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Hello All (Cond)
 public static void main(String[] args) {
 int size = args.length;
 if (size == 0) {
o S.o.p("Usage : java HelloAll n1 n2 n3 .. ");
 } else {
o for (int i = 0; i < size; i++) {
o S.o.p ( i+ " = Hello " + args[i]);
o }
 }
 }

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Hello All - switch
 public static void main(String[] args) {
 int size = args.length;
 switch(size) {
 case 0 :S.o.p("Usage : java HelloAll1 n1 n2 n3..");
o break;
 case 1 : S.o.p(“Hello “ + args[0]);
o break;
 default :
o for (int i = 0; i < size; i++) {
 S.o.p(i + " = Hello " + args[i]);
o }//for
 }//switch
 }//method

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Add.java – Integer Arguments
 public class Add {
 public static void main(String[] args) {
o int a = Integer.parseInt(args[0]);
o int b = Integer.parseInt(args[1]);
o int sum = a + b;
o System.out.println("Sum is " + sum);
 }
 }
 C:>java Add 10 20

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Division
 public class Division {
o public static void main(String[] args) {
o int a = Integer.parseInt(args[0]);
o int b = Integer.parseInt(args[1]);
o double div = a/b;
o System.out.println("Division is " + div);
o }
 }

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Define a Method
 public static void main(String[] args) {
o printAll(args);
 }// main
 public static void printAll(String[] args) {
o for (int i = 0; i < args.length; i++) {
 System.out.println(“Hello " + args[i]);
o }
 }//printAll

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Return a Value
 public static double getDivision(int a, int b)
o {
 double div = a / b;
 return div;
o }
 }

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Command line Menu
 public static void main(String[] args) throws Exception{
 int ch = System.in.read(); //Read data from keyboard
 System.out.println( "Selected char ASCII Code " + ch);
 if (ch == 'A' || ch == 'a') {
 Add.main(args);
o } else if (ch == 'D' || ch == 'd') {
 Division.main(args);
o } else {
 S.o.p("Incorrect Choice ");
o }
o }
 }

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10
One Dimension Array
20
[0]
18
..
10
8
6
4
2
[1]
[8]
[9]
[2]
[3]
[4]
[n]
length
int[] table = new int[10];
int a = table[4];
int a = table[2];
int size = table.length;

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10
Initialize an Array
20
[0]
18
..
10
8
6
4
2
[1]
[8]
[9]
[2]
[3]
[4]
[n]
length
int[] table = new int[10];
table[0] =2;
table[1] =4;
….
Or
int[] table = {2,4,6,8,10,12,14,16,18,20};

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Other Data Type Arrays
char[] chList = new char[5];
chList[0] = ‘A’….
o Or
char[] chList = {‘A’,’B’,’C’,’D’,’E’}
String[] strList = new String[5];
strList[0] = “A”
strList[1] = “Bee”
o Or
String[] strList = {“A”,”Bee”,”Cee”,”Dee”,”E”}

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Copy an Array
public static void main(String[] args) {
o char[] copyFrom = { 'd', 'e', 'c', 'a', 'f', 'f', 'e', 'i', 'n', 'a',
't', 'e', 'd' };
o char[] copyTo = new char[7];
o System.arraycopy(copyFrom, 2,
o copyTo, 0, 7);
o S.o.p(new String(copyTo));
}
Start
Index
Start
Index
No Of
Element

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One Dimension Array
int[] table;
table = new int[10];
table[0] =2;
table[1] =4;
4B
10
[0]
[1]
[9]
length
2
4
20
1000
1000
table

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10
length
2D Array
[0]
20
18
..
10
8
6
4
2
[1]
[8]
[9]
[2]
[3]
[4]
[n]
30
27
..
15
12
9
6
3
40
36
..
20
16
12
8
4
90
81
..
45
36
27
18
9
100
90
..
50
40
30
20
10
…
[0] [1] [2] [7] [8]
9
9
..
9
9
9
9
9

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int[][] table = new int[10][9];
table
1010
1000
1000
1011
1111
1010
1011
1111

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Define an Array
 int[][] table = new int[10][9];
 table[1][5] = 5;
 int size = table.length;
 int size = table[0].length;
 int[][] rows = new int[10][];
 rows[0] = new int[9];
 rows[1] = new int[19];
 rows[2] = new int[29];
 int[][][] xyz = new int[10][9][2];

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3D Array
20
[0]
18
..
10
8
6
4
2
[1]
[8]
[9]
[2]
[3]
[4]
[n]
30
27
..
15
12
9
6
3
40
36
..
20
16
12
8
4
90
81
..
45
36
27
18
9
100
90
..
50
40
30
20
10
[0] [1] [2] [8] [9]
20
18
..
10
8
6
4
2
30
27
..
15
12
9
6
3
40
36
..
20
16
12
8
4
20
18
..
10
8
6
4
30
27
..
15
12
9
6
20
18
..
10
8
6
4
2
30
27
..
15
12
9
6
3
40
36
..
20
16
12
8
4
90
81
..
45
36
27
18
9
100
90
..
50
40
30
20
10
90
81
..
45
36
27
18
9
100
90
..
50
40
30
20
10
…
[0]
[1]
[2]

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java.util.Date class
 import java.util.*;
 public class TestDate {
 public static void main(String[] args) {
o Date d = new Date();
o S.o.p("Date : " +d);
o S.o.p ("Long Time : " +d.getTime());
 }
 Output
o Date : Mon Jan 04 00:35:53 IST 2010
o Long Time : 1262545553156

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Format a Date
 import java.util.*; import java.text.SimpleDateFormat;
 public class TestDateFormat{
 public static void main(String[] args) {
o Date d = new Date();
o SimpleDateFormat format= new SimpleDateFormat("dd/MM/yyyy");
o String str = format.format(d);
o S.o.p("Date : " + str );
o String str1 = "22/03/2009";
o Date d1 = format.parse(str1);
o S.o.p(d1);
 }
 Output
o String : 04/01/2010
o Sun Mar 22 00:00:00 IST 2009

66. Disclaimer
This is an educational presentation to enhance the skill
of computer science students.
This presentation is available for free to computer
science students.
Some internet images from different URLs are used in
this presentation to simplify technical examples and
correlate examples with the real world.
We are grateful to owners of these URLs and pictures.
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67. Thank You!
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