core java - baabtra

WELCOME

Core Java

Installation

Environment setup:• Install JDK• Install eclipse

JVM, JRE, JDK

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.javaRun it->java MyClass

The process

Features of Java

Naming conventionJava 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 programs1. 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 programs1. 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 ListArrays have a fixed size

int arr[ ] = new int[10] ;

List is dynamic in nature

List<int> lst = new ArrayList<int>();

ModifiersAccess 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

Real World Objects

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 actionsI can be drived

I can consume fuelI 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 actionsI can be drived

I can consume fuelI 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 Software World

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: 20Height: 35

calculateArea(){return width*height;

}



rectangle.width=20;



Calling the method calculateArea()

rectangle

width: 20Height: 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 variablesHeightWidth

Member functioncalculateArea{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: 20Height: 35

calculateArea(){return 20*35;

}

THANK YOU

core java - baabtra

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