Java Full Course

Why You Must Learn Java?

One of the most popular languages. java Currently runs on,000 devices.

Wide usage (web Apps, Backend, Mobile, enterprise software).

High paying and lots of flexible

Object Oriented

Rich APIs and Communication Support.

What is a Programming language?

Humans use natural language like Hindi/ English.

computers only understand 0 and 1.

Giving Instructions to as a computer.

Instruction: Tell the computer what to do.

These Instructions are called codes.

Human Interaction is given in High-level languages.

Compiler converts High-level; language to Low-level Language.

What is An Algorithm?

Instructing Computer.

Step-by-step instructions to solve a particular task.

Example: instructions about How to Make Tea?

What is Syntax?

Structure of Words in a sentence.

Rules of Langauge

For Programming exact syntax must be followed.

History of Java

Developed by James Gosling at Sun Microsystems (Early and Originally named “oak”, later renamed Java in 1995)

First Release (1995): Introduced “Write Once, Run Anywhere” concept with cross-platform Compatibility.

JVM converts Byte code into Machine Code.

Developed with a vision of backward compatibility, Should break into new version releases.

Rapid Growth and Diversification: (The late 1990s -2010): Expanded from web apples to server-side applications; standardized into different editable for various computable programs.

How Java Changed The Internet?

Portability with Write Once Run Anytime.

Security because it is running on a virtual Machine.


Java is robust due to its strong memory management, exception handling, and type-checking Mechanism which helps in preventing more effective processing and Task management.

Multithreading in programming is the ability of the CPU to execute multiple threads concurrently. Allows for more efficient processing and Task Management.

Java is Architectually neural because the compiled code bytecode can run on any device with Java Virtual Machine, regardless of the Hardware Architecture.

Java combined high performance with interpretability, as its bytecode is interpreted by the Java Virtual Machine (JVM), which is just-in_time (JIT) commands for efficiency and Framework.

Java is inherently;\ distributed and designed to facilitate Network-based application development and interaction, seamlessly integrating with Internet protocols and remote method invocation.

Java is the Object object-oriented programming.

(2) Java Basics

Installing JDK

Search JDK download

Make Sure to download from the Oracle website.

Download the latest Version.

Website Address for Java Download:

(1) Programm java

(2) Java Compiler

(3) Program.class

(4) JVM

(5) Program

(6) Java Source File

(7) Javac

(8) Bytecode .class file

(9) Java

(10) Output

File Extensions


  • Contains Java Source Code
  • High-Level Human Readable
  • Used For Development
  • File is Editable


  • Contains Java Bytecode
  • For consumption of JVM
  • Used for Execution
  • Not Meant to be Edited

JDK to JVM and JRE


  • It is a software kit required to develop Java Applications.
  • Includes the JRE< an interpreter/Loader (java), a compiler (Javac), a Document(Javadoc), and other tools needed for Java Development.
  • Essentially, JDX is a superset of JRE.


  • It’s part of the JDK but can be downloaded Separately.
  • Provides the Libraries, the JVM, and other components to run the app.
  • Does not have tools and utilities for developers like compilers or interpteres.


It is part of JRE and is responsible for executing the bytecodes.

Ensure Java’s write-once-code anywhere capability.

Not Platform Independent a different JVM is needed for each type of OS.

Showing Output

System.out.println(“Three”)New Line

Importance of Main Method:

Entry Point: It’s the Entry point of a Java Program, where the execution starts, Without the main method., The Java Virtual Machine(JVM) does not know where to begin without code.

*Public and Static: The main method must be public and static, ensuring it’s and to JVM’s without needing to initiate the class.

*Fixed Signature: The main method has a fixed signature: Public static main(string[] args), Deviating from the signature means the JVM way, as the starting point.

What is IDE?

  • IDE stands for Integrated Development Environment.
  • Software Suite that consolidates basic tools required for software development.
  • The central hub for coding, finding problems, and testing.
  • Designed to improve developer efficiency.

Why We Need an IDE?

1.Streamline Development

2. Inceraes Productivity

3. Simplifies the complex tasks

4. Offers a unified Workspace

5. IDE features

  1. code Autocomplete
  2. Syntax Highlighting
  3. Version Control
  4. Error Checking

Installing IDE (Intellij Idea)

Search Intellij EDA

Make Sure download the Community Version.

Keep Your software up to date.

Download Website :

(Download Software)

You have to download the community version.

After downloading it install it on your local system.

public class Main {
  public static void main(String[] args) {

Practice Exercise:
1.Computers understand high level languages like Java , C  - > false
2. An Algorithmm is set of instructions to accomplish task -> True
3. Computer is smart enough to ignore incorrect syntax.
4. Java was released in 1992. - True
5. Jaava was named over a person who made a good coffee - false
6. Bytecode is platform Indepenedent : True
7. JDK is a part of JRE = False
8. It;s Optional to declare main method as public. = False
9. .class flle contains machine code = False (It contains Byte code)1
10, Println adds a new line at the end of the line. (true)

Data Types, variables and Input:
variables are like containers used for stroring data values.
Variables has 2 parts : varible names, value.
Variables are not of same size.

Memoey Allocation:
Every Character is Converted in the 0s and 1.
int a = 5
Every Memory is in RAM.
The storage of the variable is done in RAM.
RAM has Memory cell which has locations. 
RAM cell Stores Address and name. 

int age =20;
int - Data Type
age= Variable, name
20 - value
=  Assigment Operator
in RAM the The memory will be reserved for the variable age.
SizeDefault ValueType of value stored
byte1 Byte0.integral
short 2 Byte0Integral
int4 Byte0Integral
long8 Byte0LIntegral
char2 byte‘\U0000″Character
float4 byte0.0FDecimal
double8 byte0.0dDecimal
boolean1 bit(till JDL 1.3 uses i byte)FTrue or False

Non Primitive Data Type: String, Arrays, Objects, etc

public class Main {
public static void main(String[] args) {
int myNumber= 865; (//initlization)
int YourNumber; (//Declaration)
boolean isVegetarian=false;
float myFloat=5; )//It will consider 5.0


Naminfg Convention:

Camel case
start with a lowercase letter, Capitalize the first letter of each subsequent word.
Example: myVariableName

Starts with lowercase letter.separate words with underscorre
Example: My_variable_name

* All lowercase letters, seperate words with hyphens, Example: my variable name

Keep a Good and Short name:
Choose names that are descriptive, but not tooo long. It should make it easy to understand and variable;’s purpose.
Java uses the camel case/

Java Identifier Rules:

1. The only allowed characters for identifiers are all alphanumeric Character [AZ][az][0-9],$, and _
2.can’t use keywords or reserved words
3Identifiers should not start with digits (0-9)
4. java identifiers are case-senstive.
5. There is no limit on the length of the identifier but it is advisable to use the optimum length of 4-15 character only.

Escaping Sequence:

public class Main {

  public static void main(String[] args) {

     System.out.println(“Hello \KGcopding\…”); (//Escaping Sequence]])


Escape SequenceDescription
\tInsert a tab in the text at this point
\bInsert a backspace in the text at this point
\nInsert a newline in the text at this point
\”’Insert a double Quote Character in the text at this point
\\insert a backslash character in the text at this point.

User Input

import java.util. Scannner

public class UserInput{
  public static void main(string[] args) {
     Scanner input= new Scanner(
     System.out.println("Enter Your Name:")
     String Name=input.nextline():
,    System.out. println("Good Morning " + name)
     System.out. println(name + ", Also tell me your age)
      int age = input.nextInt();
     System.out.Println("Your age is: " + age);

Example: Create a Program to input name of the person amd respong with "Welcome to KG Coding"

public class welcome{
   public static void main (String[] args) {
        System.out.print("please enter your name: "):
          scanner input = new Scnner(
          String name = input.Nextline():
         System.out.printLn("welcome" + name + "KG coding)



Example: Write a program to add Two Numbers (sum)
public class Sum {
   Public static void man (String[] args{
       scanner input = new Scanner(
       System.out.printlln("Welcome to Our calculator");
        int firt num = input.nextint();
        System.out.print("Now.Please Enter the second Number: ");
        int sum = First Name + Second Num 
        System.out.print("Now.Please Enter the second Number: ");

Type Conversion and casting

Automatic Type Conversion 
(Wideling - Implicit)

byte -> Short -> int -> long -> Float -> double 

 Narrowing (explicit)
 byte  <- Short <- int -< long <- float <- double 

public class TypeConversion {
  public static void main (String[] args) {
         float my float =5;
         System. out.Println(myFloat);
         int myInt= (int) 5.45
         System. out.Println(myInt);

Question Answer
In Java, a variable’s name can start with a number False
Char in Java can store a single characterTrue
Java variable names are case-sensitive False
100l is a valid literal in JavaTrue
\d is an escape sequence in Java for digit Character false
Scanner class is used for trading console input True
In Java, an int can be automatically converted to a ByteTrue
In java, an int can be automatically converted to a ByteTrue
Scanner class can be used to read both primitive datatypes and strings True

Operator, If – Else & Number System

Assignment operator (=)

Assigns the tight hand operand’s value to the left-hand operand.

Example int a =5;

public class main {

public static void main (string[] args) {

int myInt=9;

int newInt = myInt;

System. out.println(newInt);



Example: Create a Program to Swap two numbers:

Public class Swap (
       Public static Void main (String[] args) {
            scanner.input=new Scanner(System,in)
            System.out.println("Welcome to swapping station \n\n");
            int a =;
            System.out.println("Entern the value of A");
             int b =;
             System.out.println("Entern the value of A");

Arithmetic Operator

%Modulus Operator to ger remainder target division 5%21

Public class Arithmatic {
public static void main (String[] args){
int a =8;
int b=22;

Unary operators

Pre Incrementx=x+y
pre Decrementx= –y
Post Incrementx=y++
Post Decrementx= y–

# If-Else Operator

If else:

  1. Syntax : uses if () {} to check a condition
  2. What is if : Executes Block if condition is True, Skips if false.
  3. What is else : Executes a block when the if condition is false.
    4.Curly Braces can be ommited for single statements, but not recommended
  4. If -else ladder : Multiple if and else if blocks, only one executes.
  5. Use Variable : Can store conditions in Variables for use in if statements.

public class LearningIf {

public static void main (String [] args) {
boolean isMale= true:
String name = “Bob”

     if (isMale) {
       System.out.println ("Mr," + name);
      } else {
        System.out.Println (:Mr." + name)    
       System.out.println("After if")


Or You can write this as this:

public class LearningIf {

public static void main (String [] args) {
boolean isMale= true:
String name = “Bob”

if (is Male) System.out.println(“Mr.” + name);
else System.out.Println(“Ms.” + name)
System.out.println(“After if”)

boolean is SeniorCitizen {
system.out.println(“Hello Senior Citizen)

if(isSeniorCitizen) {
System.out.println(“Hello Senior Citizen”)
} else if{
if(isAnAdult) {
System.out.println(“Hello Audit”)
} else {
System.out.println(“Hello Child”)

Relational Operators :

== Check Values Quality
=== Checks Vale and Type

in Equality
!= Checks value inequality


Greater than
< Less than
= Greater than Equal to
<= Less than Equal to

The order of Relational Operators is less than arithmetic operators.

public class Relational {
public static void main (String[] args) {
Scanner.input = new Scanner (
System.out.println(“Welcome to Driving License Portal”)
int age = input.nextint()

  if(age>=18) {
    system.out.println("You are eligible to ride")
  } else {
    system.out.println("Beta Cycle Chala")


Logical Operators :

  1. Types : && (AND), || (OR) , !(NOT)
  2. AND (&&) : All Conditions must be true for the result to be true.
  3. Of(||): only one condition must be true for the result to be true.
  4. NOT(!) : inverts the Boolean Value of the condition.
  5. Lower Priority than Math and Comparison Operators.

Public class Logical {
public static void main ( String [] args) {
scanner input = new Scanner(
sytem.out.println(“Welcome to Ticket Discount Calculator”)
sytem.out.println(“Please Enter Your age”)
int age = input.nextInt();
System.Out.println(“Are you a female? (true/false) “);
boolean ifFeamle = inpur.nextBoolean();

  if(age<5) {
    System.out.println("You got 50% Discount) 
    } elseif  { (age >60) && !isFemale) {
    System.out.println("You got 25% Discount)
   } else {
     System.out.println("You got 25% Discount)
Number SystemBase Or RedixDigits or Symbols

Decimal Number System:

* Decimal Number System is base-10 System that has ten digits : 0,1,,6,7.8.9
* The Decimal Number System is said to base, or radix, 10 because tt uses 10 digits and the coefficients are multiplied by 10.
* This is the base that we often use in our day-to-day life.
* Example (7.392) 10, Where 7,392 is a shorthand Notification for what should be written.

Binary Number System

  • Binary Number System:
  • The coefficients of the binary number system have only two possible values: 0 and 1.
  • Each coefficient a, is multiplied by a power of the radix, e.g. 2!, and the results are added to
  • obtain the decimal equivalent of the number.
  • Example (11010.11)2 Value in Decimal?

What is Loop?

  1. Code that runs multiple times based on condition.
  2. Repeated Execution of code.
  3. Loops Automate repetitive Tasks.
  4. Types of Loops: While, For, While, do- while
  5. Iterations: Number of times loops run

Types of Loops

(1) While Loop



While(glass is not empty) {

drink water


while(sleep not) {

continue sleep


print the sum of n natural numbers: 
import java.util.Scanner;

public class SumOfNaturalNumbers {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(;
        System.out.print("Enter the value of n: ");
        int n = scanner.nextInt();
        int sum = sumOfNaturalNumbers(n);
        System.out.println("The sum of the first " + n + " natural numbers is: " + sum);
    public static int sumOfNaturalNumbers(int n) {
        return (n * (n + 1)) / 2;

Number Systems

  • Printing Pattern
  • Triangular Patterns
  • Numerical Rectangular Pattern
  • Numerical Triangular pattern

System to represent numbers in different forms with different base values.

color code and Memory Allocation – Hexa Decimal Number System (0-15)

Base 10 – Decimal Numbers

245 = 2 * 10^2 + 4 * 10 ^ 1 + 5 * 10^1

Base 2 – Binary Number Systems (0-1)

1001 = 1 * 2^3 + 0* 2^2 + 0 * 2^1 + 1* 2^0 = 8 +0 + 1 = 9

Public class binaryToDecimal{

Public static void main (string[] args]

Scanner sc = new Scanner(

int binary – num = sc.nextInt():

int ans=0;

int pw=1;

while(binary_num >0) {

int unit_digit = binary_ num % 10

and + (unit_digit* pw)

binary num /=10






Object Oriented Programming



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