Core java - baabtra

Installation
Environment setup:
• Install JDK
• Install eclipse

First java program
First Java Program
public class MyClass{
public static void main(String[] args){
System.out.println(“Hello baabtra”);
}
}
Compile the program
->javac MyClass.java
Run it
->java MyClass

Naming convention
Java follows camelcase syntax for naming
Type Convention
Class Should start with uppercase letter and be a noun e.g. String,
Color, Button, System, Thread etc.
Interface Should start with uppercase letter and be an adjective e.g.
Runnable, Remote, ActionListener etc.
Method Should start with lowercase letter and be a verb e.g.
actionPerformed(), main(), print(), println() etc.
Variable Should start with lowercase letter e.g. firstName, orderNumber
etc.
Package Should be in lowercase letter e.g. java, lang, sql, util etc.
Constants Should be in uppercase letter. e.g. RED, YELLOW,
MAX_PRIORITY etc.

Basic Data types
Type Size Max Value Min Value Default
boolean 1 True/ False False
byte 8 -128 127 0
short 16 -215 215-1 0
int 32 -232 232-1 0
long 64 -264 264-1 0L
float 32 -232 232-1 0.0f
double 64 -264 264-1 0.0d
Char 16 0 FFFF

Loops and Control Structures
• while
• do … while
• for
• If
• If … else
• switch … case

Java programs
1. Write a java program to check given number is even or odd
2. Write a java program to print series of even numbers between 100
and 150
3. Write a java program to find sum of numbers divisible by 9 between
500 and 1000
4. Write a java program to find factorial of a given number
5. Write a java program to reverse a string
6. Write a java program to find whether the given string is palindrome or
not
7. Write a java program to find the sum of prime numbers below 100
8. Write a java program to find area and perimeter of a circle
9. Write a java program to find area and perimeter of a square
10.Write a java program to sort 3 numbers

Java programs
1. Write a java program to add 10 numbers to an array and sort it in
ascending order
2. Reverse number
3. Add two matrices
4. Display current system date and time
5. swap two numbers
6. Count total number of words in a string
7. Count divisors of an interger number
8. Print multiplication table
9. Save given string to a file

Java programs
• Write a java program to print following patterns
1 2 3 4
*
* *
* * *
* * * *
* * * *
* * *
* *
*
*
* * *
* * * * *
* * * * * * *
*
* *
* * * *
* * * * *

Array and List
Arrays have a fixed size
int arr[ ] = new int[10] ;
List is dynamic in nature
List<int> lst = new ArrayList<int>();

Modifiers
Access Modifiers
• default - Visible to package
• public - Visible everywhere
• private - Visible inside the class
• protected - Visible to package and all subclasses
Non Access modifiers
• static
• final
• abstract

Methods
modifier returnType nameOfMethod (Parameter List) {
// method body
}
Create a class Calculator with methods add, subtract,
multiply and divide. Use it from main method in different
class.

OOP Concepts
• Object-oriented programming (OOP) is a style of
programming that focuses on using objects to design and
build applications.
• Think of an object as a model of the concepts, processes, or
things in the real world that are meaningful to your
application.

Objects in real world
• Object will have an identity/name
▪ Eg: reynolds, Cello for pen. Nokia,apple for mobile
• Object will have different properties which describes them
best
▪ Eg:Color,size,width
• Object can perform different actions
▪ Eg: writing,erasing etc for pen. Calling, texting for
mobile

Objects
I have an identity:
I'm Volkswagen
I have different properties.
My color property is green
My no:of wheel property is 4
I can perform different actions
I can be drived
I can consume fuel
I can play Music
I have an identity:
I'm Suzuki
I have different properties.
My color property is silver
My no:of wheel property is 4
I can perform different actions
I can be drived
I can consume fuel
I can play Music

How these objects are created?
• All the objects in the real world are created out of a basic
prototype or a basic blue print or a base design

Objects in the Software World
• Same like in the real world we can create objects in computer
programming world
– Which will have a name as identity
– Properties to define its behaviour
– Actions what it can perform

How these Objects are created
• We need to create a base design which defines the
properties and functionalities that the object should have.
• In programming terms we call this base design as Class
• Simply by having a class we can create any number of
objects of that type

Definition
• Class : is the base design of objects
• Object : is the instance of a class
• No memory is allocated when a class is created.
• Memory is allocated only when an object is created.

How to create Class in Java
public class Shape
{
private int int_width;
private int int_height;
public int calculateArea()
{
return int_width * int_height;
}
}

public class Shape
{
{
return int_width*int_height;
}
}
Is the access specifier

public class Shape
{
{
return int_width* int_height;
}
}
Is the keyword for
creating a class

public class Shape
{
{
return int_width*int_height;
}
}
Is the name of the class

public class Shape
{
{
return int_width* int_height;
}
}
Are two variable that
referred as the
properties. Normally
kept private and access
using getters and
setters. We will discuss
getters and setters later
in this slide

public class Shape
{
{
return int_height*int_width;
}
}
Is the only member
function of the class

How to create Objects in Java
Shape rectangle = new Shape();
rectangle.int_width=20;
rectangle.int_height=35;
rArea=rectangle.calculateArea();
This is how we create an
object in java
rectangle
Height:
width:
calculateArea()
{
return height*width;
}

rectangle.width=20;
rectangle.height=35;
Is the class name

Is the object name which
we want to create

“new” is the keyword
used in java to create an
object

What is this???
It looks like a function
because its having pair of
parentheses (). And also
its having the same name
of our class . But what is it
used for ??
We will discuss it soon .
Just leave it as it is for
now

rectangle.width=20;
Setting up the property
values of object
“rectangle”
rectangle
width: 20
Height: 35
calculateArea()
{
return width*height;
}

rectangle.width=20;
Calling the method
calculateArea()
rectangle
width: 20
Height: 35
calculateArea()
{
return 20*35;
}

Example
Class : Shape
Height:35
width:20
Object rectangle
calculateArea()
{
Return 20*35
}
Height:10
width:10
Object square
calculateArea()
{
Return 10*10;
}
Member variables
Height
Width
Member function
calculateArea
{
return height*width;
}

What we just did was?
• Created an object
Same like we declare variable.
eg: int a;
• And assigned values for it
recangle.int_height=35;
Same like we assign variable value.
eg: a=10;
Rectangle
Width:
Height:
calculateArea()
{
return
width*height;
}
Rectangle
width: 20
Height: 35
calculateArea()
{
return 20*35;
}

Core java - baabtra

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