Java Basic Concepts – A Beginner’s Guide

 

                                                                            

Java is one of the most popular programming languages in the world. It is simple, platform-independent, and widely used in software development. If you are new to programming, learning Java basics will give you a strong foundation. Let’s explore the key concepts step by step:

1. What is Java?

Java is a high-level, object-oriented, and platform-independent programming language developed by Sun Microsystems (now owned by Oracle).
- High-level → Easy to read and understand.
- Object-oriented → Based on real-world objects (like Car, Student, BankAccount).
- Platform-independent → "Write once, run anywhere" using JVM (Java Virtual Machine).

2. Features of Java

- Simple – Easy to learn compared to other programming languages.
- Object-Oriented – Focuses on objects rather than functions.
- Platform Independent – Works on Windows, Mac, Linux, etc.
- Secure – Provides strong memory management and security features.
- Robust – Handles errors and exceptions smoothly.
- Multithreaded – Supports multiple tasks running at the same time.

3. Java Architecture

When you write and run Java code:
1. Source Code (.java file) → Written by the programmer.
2. Compiler (javac) → Converts Java code into Bytecode (.class file).
3. JVM (Java Virtual Machine) → Runs the bytecode on any platform.

This makes Java platform-independent. ✅

4. Basic Java Syntax Example

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

Explanation:
- public class HelloWorld → Defines a class.
- main(String[] args) → Entry point of any Java program.
- System.out.println() → Prints output to the screen.

5. Variables in Java

Variables are containers that store data values.
Example:

int age = 25;        // Integer type
double price = 99.9; // Decimal number
String name = "John"; // Text

6. Data Types in Java

- Primitive Data Types: int, char, float, double, boolean, byte, short, long.
- Non-Primitive Data Types: String, Arrays, Classes, Objects.

7. Operators in Java

Operators are symbols used to perform operations:
- Arithmetic Operators → + , - , * , / , %
- Relational Operators → == , != , > , < , >= , <=
- Logical Operators → && , || , !

8. Control Statements in Java

Used to control the flow of a program:
- if-else – Decision making
- switch – Multiple conditions
- for loop – Repeats a block of code
- while loop – Runs until condition is true
- do-while loop – Executes at least once

Example:

int num = 5;
if(num > 0){
    System.out.println("Positive Number");
} else {
    System.out.println("Negative Number");
}

9. Object-Oriented Concepts in Java

Java is built on OOPs (Object-Oriented Programming System).
The four main pillars are:
1. Encapsulation – Wrapping variables & methods into a single unit (class).
2. Inheritance – One class inherits properties of another.
3. Polymorphism – Same method behaves differently (overloading & overriding).
4. Abstraction – Hiding implementation details and showing only functionality.