Java Basics

www.SunilOS.com 1
JAVA BASICS
www.sunilos.com
www.raystec.com

www.SunilOS.com 2
Java is a Programming Language
Java is a programing language.
just like any other primitive language such
as C, C++, Pascal.
It has
o Variables
o Functions
o Data Type
o Control Statement
o Arrays

www.SunilOS.com 3
Java is OOP
3 Idiot
Java is Object Oriented Programming .
follows OOP methodology.
Java thinks only Objects.
Meri
4 Lakh
ki watch
Just like a Money Oriented Person
who always thinks of Money.

www.SunilOS.com 4
Basic Unit of Java is Object
Such as program of
o sum of two numbers is an object
o Fibonacci Series is an object
o SMS Services is an object
o Email Services is an object
o Account Services is an object
Basic unit of Java is an Object.

Expert Object
Each Object is an Expert object.
Expert object contains related variables and
functions.
www.SunilOS.com 5

An Expert never overlaps responsibilities
www.SunilOS.com 6
Creator
Preserver
Destroyer
Trimurti

Experts bring Modularity and Reusability
www.SunilOS.com 7

www.SunilOS.com 8
Object has State & Behavior
Object has state and behavior.
State will be changed by behavior.

www.SunilOS.com 9
Object has State & Behavior
States are stored in memory variables.
Behavior changes states.
Behaviors are implemented by functions;
functions are referred as methods in OOP
Variables and Methods of an object are
defined by Class.
Class is the structure or skeleton of an
Object.

Class vs Objects
www.SunilOS.com 10
Realization
Realization
State/Variables
currentGear
Speed
Color
Methods
changeGear()
Accelerator()
break()
changeColor()
State/Variables
name
address
Methods
changeName()
changeAddress()
Design
Real world entities based
on design

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.
www.SunilOS.com 11

www.SunilOS.com 12
Class
Class contains methods and variables.
Variables contain values of type int,
float, boolean, char and String.
Methods perform operations.

Executable Class
An executable Class must have default
method ‘main’ .
Method main() is the entry point of a class.
main() is called by JVM at runtime.
www.SunilOS.com 13

www.SunilOS.com 14
Program
Program Structure - Primitive Language
int i = 5 //global variable
void main(){
..
a(5);
}
void a(int k){
int j = 0; //local variable
..
}

www.SunilOS.com 15
Primitive Language Library
Library
Program 1 Program 2
Program 3 Program 4
 Library is made of multiple reusable programs.

www.SunilOS.com 16
Class
Program Structure - Java
int i = 5 //global variable
void main(){
..
a(5);
}
void a(int k){
int j = 0; //local variable
..
}

www.SunilOS.com 17
Java Library - API
Package
Class 1 Class 2
Class 3 Class 4
 Package is made of related classes.

www.SunilOS.com 18
JAVA Application
ApplicationApplication
Package 1 Package 2
Package 3 Package 4
 Application is made of multiple packages

www.SunilOS.com 19
Java Program is a Class
public class HelloJava {
…
}
A class may contain multiple variables and
methods.
A Class should have default ‘main’ method that is
called by JVM at the time of execution.

www.SunilOS.com 20
My First Program - HelloJava
public class HelloJava {
opublic static void main(String[] args) {
o String name =“Vijay”;
o System.out.println("Hello “ + name);
o}
}
public, class, static, and void are keywords.
Keywords are always written in small letters.

www.SunilOS.com 21
Keywords
class – is used to define a class.
public – Access modifier shows accessibility of a
class or variable or method to other Java classes.
There are 3 access modifiers public, protected and
private.
static – Memory for the static variables is
assigned only once in life. Non-static variables are
called instance variables.
void – is a NULL return type of main method.

www.SunilOS.com 22
Statements
System.out.println() method is used to write text at
standard output device – Console.
String is a data type.
Two strings are concatenated by + operator
o String name = “Vijay” ;
o “Hello” + name is equal to “Hello Vijay”.

www.SunilOS.com 23
JAVA_HOME
 Java is installed at “C:Program FilesJavajdkx.x.”
 It is known as JAVA_HOME
 JAVA_HOMEbin folder contains
o javac.exe – Java Compiler
o java.exe – JVM ( Java Virtual Machine)

www.SunilOS.com 24
Compile Program
Open command prompt
Create c:sunrays
Change directory to c:sunrays
Compile program by
o javac HelloJava.java
o It will create HelloJava.class
Execute class file by
o java HelloJava

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

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

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

www.SunilOS.com
Control Statement
if-else
while
for
do-while
GOTO
28

www.SunilOS.com
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 नाचूंगी !!!");
 round++;
 if(round>500 )
• जबतकहेजान = false;
 }
 }
 }
30

www.SunilOS.com
For Loop 10$ for 5 shots
How Much?
Okay!!
31

 public class HelloFor {
 public static void main(String[] args)
 {
o for (int shot=1; shot <= 5; shot++)
o {
 System.out.println(i+“Shot Balloon");
o }
o }
 }
www.SunilOS.com
For Loop – Five shots
32

www.SunilOS.com 33
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 }
}

www.SunilOS.com 34
Print Hello Java 5 times - while
public class HelloWhile {
o int i = 0;
o while (i < 5) {
 System.out.println("Hello Java ");
 i++; // i = i+1
o }
}
}

www.SunilOS.com 35
Print Hello Java 5 times – do-while
public class HelloDoWhile {
int i = 0;
o do {
 System.out.println( i+ " Hello Java ");
 i++;
o } while (i < 5);
}
}

www.SunilOS.com 36
Foreach statement
public class HelloFor {
o int[] table={ 2, 4, 6, 8, 10};
o for (int v : table) {
 System.out.println(“Table “ + v);
o }
o }
}

www.SunilOS.com 37
Add.java
public class Add {
oint a = 5;
oint b = 10;
oint sum = a + b;
oSystem.out.println("Sum is " + sum);
}
}

www.SunilOS.com 38
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

www.SunilOS.com 39
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(" All a is replaced by b- “ + name.replaceAll("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

www.SunilOS.com 40
Java.lang.StringBuffer class
 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());

www.SunilOS.com 41
String vs StringBuffer
String is immutable
o Memory object can not be changed.
StringBuffer is mutable
o Memory object can be changed.

www.SunilOS.com 42
java.lang.Math class
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

www.SunilOS.com 43
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));

www.SunilOS.com 44
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.

www.SunilOS.com 45
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

www.SunilOS.com 46
Hello Name – if <condition>
 public class HelloName1 {
o if (args.length == 1) {
 System.out.println("Hello " + args[0]);
o } else {
 System.out.println(“Parameter name is required");
o }
 }
 }

www.SunilOS.com 47
Hello All
public class HelloAll {
o for (int i = 0; i < args.length; i++) {
 System.out.println(i + " = Hello " + args[i]);
o }
}
}

www.SunilOS.com 48
Hello All (Cond)
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 }
}
}

www.SunilOS.com 49
Hello All - switch
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]); break;
default :
o for (int i = 0; i < size; i++) {
 S.o.p(i + " = Hello " + args[i]);
o }//for
}//switch
}//method

www.SunilOS.com 50
Add.java – Integer Arguments
public class Add {
oint a = Integer.parseInt(args[0]);
oint b = Integer.parseInt(args[1]);
oint sum = a + b;
oSystem.out.println("Sum is " + sum);
}
}
C:>java Add 10 20

www.SunilOS.com 51
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 }
 }

www.SunilOS.com 52
Define a Method
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

www.SunilOS.com 53
Return a Value
 public static double getDivision(int a, int b)
o {
 double div = a / b;
 return div;
o }
 }

www.SunilOS.com 54
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 }
 }

www.SunilOS.com 55
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;

www.SunilOS.com 56
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};

www.SunilOS.com 57
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”}

www.SunilOS.com 58
Copy an Array
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

www.SunilOS.com 59
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

www.SunilOS.com 60
10length
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

www.SunilOS.com 61
int[][] table = new int[10][9];
table
1010
1000
1000
1011
1111
1010
1011
1111

www.SunilOS.com 62
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];
 int[][][] xyz = new int[10][9][2];

www.SunilOS.com 63
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]

www.SunilOS.com 64
java.util.Date class
 import java.util.*;
 public class TestDate {
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

www.SunilOS.com 65
Format a Date
 import java.util.*; import java.text.SimpleDateFormat;
 public class TestDateFormat{
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

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.
www.SunilOS.com 66

Thank You!
www.SunilOS.com 67
www.SunilOS.com

Java Basics

More Related Content

What's hot

Viewers also liked

Similar to Java Basics

More from Sunil OS

Recently uploaded

In this document

Java Basics