Java Programming Tutorial – Learn Java from Scratch

Tutorial 1: Introduction to Java

Java is a high-level, object-oriented programming language developed by Sun Microsystems. It was initiated by James Gosling and officially released in 1995 as a core component of the Java platform.

Java is widely used for developing:

Desktop applications
Web applications
Mobile applications
Enterprise software
Cloud-based systems

Tutorial 2: Features of Java

Object-Oriented Programming (OOP)
Platform Independence
Robust and Secure
Multithreading and Concurrency
Rich API and Standard Libraries
Framework Support
Open-Source Libraries
Maintainability and Scalability
High Performance

Tutorial 3: Hello World Program

public class Main {
  public static void main(String[] args) {
    System.out.println("Hello World");
  }
}

public class Main {
  public static void main(String[] args) {
    System.out.println("Hello World");
  }
}

Tutorial 4: Java Comments

Comments can be used to explain Java code and to make it more readable. It can also be used to prevent execution when testing alternative code.

Single-line comments

public class Main {
  public static void main(String[] args) {
    // This is a comment - Single-line Comments
    System.out.println("Hello World");
  }
}

public class Main {
  public static void main(String[] args) {
    // This is a comment - Single-line Comments
    System.out.println("Hello World");
  }
}

Multi-line comments

public class Main {
  public static void main(String[] args) {
    /* 
    Java Multi-line Comments
    System.out.println("Hello 1");
    System.out.println("Hello 2");
    
    */
    System.out.println("Hello World");
  }
}

public class Main {
  public static void main(String[] args) {
    /* 
    Java Multi-line Comments
    System.out.println("Hello 1");
    System.out.println("Hello 2");
    
    */
    System.out.println("Hello World");
  }
}

Tutorial 5: Variables in Java

Variables are used to store data in a program.

In Java, a variable is a container that holds values during program execution.

dataType variableName = value;

int age = 25;
String name = "John";
double salary = 45000.50;

dataType variableName = value;

int age = 25;
String name = "John";
double salary = 45000.50;

Rules for Naming Variables

Variable names should start with a letter, $, or _
Cannot start with a number
Cannot use Java keywords
Use meaningful names

public class VariablesDemo {

    public static void main(String[] args) {

        int age = 25;
        String name = "Kapoor";

        System.out.println(age);
        System.out.println(name);
    }
}

public class VariablesDemo {

    public static void main(String[] args) {

        int age = 25;
        String name = "Kapoor";

        System.out.println(age);
        System.out.println(name);
    }
}

Tutorial 6: Data Types in Java

Data types define the type of data a variable can store in Java.

Types of Data Types in Java

Java data types are divided into:

Primitive Data Types
Non-Primitive Data Types

Data Type	Size	Example
byte	1 byte	10
short	2 bytes	100
int	4 bytes	5000
long	8 bytes	100000L
float	4 bytes	10.5f
double	8 bytes	20.99
char	2 bytes	‘A’
boolean	1 bit	true

int age = 25;
double salary = 45000.50;
char grade = 'A';
boolean status = true;

int age = 25;
double salary = 45000.50;
char grade = 'A';
boolean status = true;

2. Non-Primitive Data Types

Non-primitive data types store references to objects.

Examples:

String
Array
Class
Interface

String name = "Java";
int[] numbers = {1, 2, 3};

String name = "Java";
int[] numbers = {1, 2, 3};

Important Points

int is the most commonly used integer type
double is used for decimal values
char stores single characters
boolean stores true or false values
String is widely used for text data

public class DataTypesDemo {

    public static void main(String[] args) {

        int age = 25;
        double salary = 55000.75;
        char grade = 'A';
        boolean passed = true;
        String name = "Kapoor";

        System.out.println(age);
        System.out.println(salary);
        System.out.println(grade);
        System.out.println(passed);
        System.out.println(name);
    }
}

public class DataTypesDemo {

    public static void main(String[] args) {

        int age = 25;
        double salary = 55000.75;
        char grade = 'A';
        boolean passed = true;
        String name = "Kapoor";

        System.out.println(age);
        System.out.println(salary);
        System.out.println(grade);
        System.out.println(passed);
        System.out.println(name);
    }
}