The document provides an introduction to Java programming, covering basic concepts such as classes, variables, and data types. It includes examples of Java programs that demonstrate various programming constructs like loops, arrays, and string manipulation. The presentation serves as an educational tool for computer science students, enhancing their programming skills with practical examples.

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JAVA BASICS
Core Concepts
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Java Program is a Class
public class HelloJava {
…
}
A class may contain multiple attributes (variables) and
methods (functions).
An executable class will have default ‘main’ method
that is called by JVM to execute the program.

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My First Program - HelloJava
public class HelloJava {
o public static void main(String[] args) {
o System.out.println("Hello Java”);
o }
}
public, class, static, and void are keywords.
Keywords are always written in small letters.
System.out object represents console

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Define a variable
public class HelloJava {
o public static void main(String[] args) {
o String name = “Vijay”;
o System.out.println(name);
o }
}

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Data Types
int
long
byte
short
float
double
1
2
4
8
4
8
-128, +127
-9.223E18, +9.223E18
-32768, +32767
-2147483648, +2147483647
+3.4 E+38
+1.7 E+308
Type Size Byte Range
char 2 0, 65535
boolean 1 true, false
0
0
0
0
0
0
0
false
Default

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Add two numbers
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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Can I buy Pizza ?
public class Add{
 public static void main(String[] args) {
o int rs = 110;
o if( rs > 100 ){
o System.out.println(“Wow! I can buy Pizza ”);
o }else{
o System.out.println(“Oh! I can not buy Pizza ”);
o }
o }
}

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Other operators
()
++
--
!
~
instance of
*
/
%
+
-
<<
>>
>>>
<
>
<=
>=
==
!=
&
^
|
&&
||
?:
=
op=

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

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

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

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10
List of elements a.k.a. Array
20
[0]
18
..
10
8
6
4
2
[1]
[8]
[9]
[2]
[3]
[4]
[n]
length
int[] list = new int[10];
list[0] =2;
list[1] =4;
….
Or
int[] list = {2,4,6,8,10,12,14,16,18,20};

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

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Handle a String
 String name = "Vijay Dinanath Chouhan";
 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

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Mathematical operations
 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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Handle a date
 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

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Command line argument
 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

19. 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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20. Thank You!
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