Java Programming Complete Tutorial

Beginner to Advanced

Java Programming Language Tutorial

Master Java programming from basic syntax to advanced Object-Oriented Programming (OOP), Collections Framework, Multithreading, and modern Java features with practical examples.

Platform Independent

Write Once, Run Anywhere

OOP & Collections

Robust Framework

Enterprise Ready

Used in Enterprise Apps

1. Introduction to Java Programming

Java is a high-level, class-based, object-oriented programming language developed by Sun Microsystems (now owned by Oracle). It was designed to have as few implementation dependencies as possible, making it platform-independent with the "Write Once, Run Anywhere" (WORA) capability.

History of Java

1991: James Gosling starts "Oak" project
1995: Renamed to Java, first public release
1996: JDK 1.0 released
2004: J2SE 5.0 (major features added)
2014: Java 8 (Lambda expressions)
2017, 2018, 2021: Java 9, 11, 17 LTS releases

Why Learn Java?

Platform Independent (WORA)
Object-Oriented Programming
Rich API and Libraries
Used in Android Development
Enterprise Applications
Strong Memory Management

First Java Program

Every Java program must have a main() method. Here's the traditional "Hello, World!" program:

HelloWorld.java

// Simple Java Program
public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

2. Basic Syntax and Structure

Java programs are composed of classes, methods, variables, and statements following a specific syntax.

Component	Description	Example
Class Declaration	Blueprint for creating objects	`public class MyClass { }`
Main Method	Entry point of Java program	`public static void main(String[] args)`
Variables	Named storage locations	`int count = 10;`
Methods	Blocks of code that perform tasks	`void display() { }`
Statements	Instructions that perform actions	`System.out.println("Hello");`
Comments	Explanatory text ignored by compiler	`// Single line comment`

Best Practice: Follow Java naming conventions: Class names in PascalCase, method/variable names in camelCase, constants in UPPER_CASE.

3. Java vs C++ vs Python

Feature	Java	C++	Python
Type	Compiled & Interpreted	Compiled	Interpreted
Memory Management	Automatic (Garbage Collection)	Manual	Automatic
Performance	High	Very High	Moderate
Platform	Platform Independent	Platform Dependent	Platform Independent
Syntax	Verbose	Complex	Simple & Readable
Use Cases	Enterprise, Android	System, Game Dev	AI, Web, Scripting

Choosing a Language:

Java: Enterprise applications, Android development, large-scale systems
C++: System programming, game development, performance-critical applications
Python: Data science, machine learning, web development, scripting

4. Running Java Programs

Windows Setup

Using JDK (Recommended):

Download JDK from Oracle website
Set JAVA_HOME environment variable
Add Java to PATH: %JAVA_HOME%\bin
Verify: java -version and javac -version

Compile & Run (Windows)

# Compile Java file
javac HelloWorld.java

# Run compiled class
java HelloWorld

# With command line arguments
java HelloWorld arg1 arg2

Linux/Mac Setup

# Install OpenJDK
sudo apt install openjdk-17-jdk

# Set environment variables
export JAVA_HOME=/usr/lib/jvm/java-17-openjdk
export PATH=$PATH:$JAVA_HOME/bin

# Compile and run
javac HelloWorld.java
java HelloWorld

30-Day Java Learning Roadmap

1-7

Week 1: Java Fundamentals

Syntax, Data Types, Operators, Basic I/O

8-14

Week 2: Control Flow & Methods

Conditionals, Loops, Methods, Arrays

15-21

Week 3: Object-Oriented Programming

Classes, Objects, Inheritance, Polymorphism

22-30

Week 4: Advanced Topics

Collections, Exception Handling, File I/O

5. Variables, Constants and Data Types

Java has two categories of data types: primitive types and reference types. Variables must be declared before use.

Variables Example

public class DataTypesExample {
    public static void main(String[] args) {
        // Primitive data types
        int age = 25;
        float salary = 45000.50f;
        double pi = 3.1415926535;
        char grade = 'A';
        boolean isEmployed = true;
        byte smallNumber = 100;
        short mediumNumber = 32000;
        long bigNumber = 1000000000L;
        
        // Constants (use final keyword)
        final double PI = 3.14159;
        final int MAX_USERS = 1000;
        
        // Reference types
        String name = "John Doe";
        
        // Display values
        System.out.println("Age: " + age);
        System.out.println("Salary: " + salary);
        System.out.println("Grade: " + grade);
        System.out.println("Is Employed: " + isEmployed);
        System.out.println("Name: " + name);
        System.out.println("PI Constant: " + PI);
    }
}

Data Type	Size (Bytes)	Range	Default Value
`byte`	1	-128 to 127	0
`short`	2	-32,768 to 32,767	0
`int`	4	-2³¹ to 2³¹-1	0
`long`	8	-2⁶³ to 2⁶³-1	0L
`float`	4	±3.4e-38 to ±3.4e38	0.0f
`double`	8	±1.7e-308 to ±1.7e308	0.0d
`char`	2	0 to 65,535	'\u0000'
`boolean`	1 bit	true/false	false

Variable Naming Rules:

Cannot start with a digit
Can contain letters, digits, underscore (_), dollar sign ($)
Cannot be Java keywords
Case-sensitive
Use meaningful names (camelCase for variables)

Next: Java Keywords