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🔹 Introduction

Java Programming Fundamentals cover the core concepts needed to begin writing Java applications. This includes understanding the structure of a Java program, syntax rules, variables, data types, operators, input/output, control structures, and the program execution flow. Mastering these basics is essential before moving to OOP concepts such as classes, inheritance, and polymorphism.

1️⃣ Structure of a Java Program

A basic Java program consists of the following elements:

• Package declaration (optional)
• Import statements (optional)
• Class definition
• Main method – entry point of execution

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

main() method syntax:

• public – accessible by JVM
• static – no object needed to invoke
• void – returns nothing
• String[] args – command-line arguments

2️⃣ Java Syntax Rules

• Java is case-sensitive: Main ≠ main
• Class names start with uppercase letters
• Method/variable names start with lowercase
• Statements end with semicolons ;
• Blocks are enclosed in curly braces { }
• Whitespace is ignored except in string literals

3️⃣ Java Variables & Data Types

Variables store data in memory. In Java, all variables must be declared with a type.

✔ Primitive Data Types

✔ Non-Primitive Data Types

• String
• Arrays
• Classes
• Interfaces
• Objects

4️⃣ Java Operators

✔ Arithmetic Operators

+ , - , * , / , %

✔ Relational Operators

== , != , > , < , >= , <=

✔ Logical Operators

&& , || , !

✔ Assignment Operators

=, +=, -=, *=, /=

✔ Increment & Decrement

++variable, variable++, --variable

5️⃣ Input & Output in Java

✔ Printing Output

System.out.println("Hello");   // Prints with newline
System.out.print("Hi");       // Prints without newline

✔ Taking Input using Scanner

import java.util.Scanner;

Scanner sc = new Scanner(System.in);
int num = sc.nextInt();
String name = sc.nextLine();
double value = sc.nextDouble();

6️⃣ Control Statements

✔ Conditional Statements

• if
• if-else
• nested if
• switch-case

✔ Looping Statements

• for loop
• while loop
• do-while loop
• enhanced for loop

✔ Jump Statements

• break
• continue
• return

7️⃣ Arrays in Java (Basic)

Arrays store multiple values of the same type in a single variable.

int[] arr = new int[5];
arr[0] = 10;
arr[1] = 20;

Or directly:

int[] marks = {90, 85, 88, 76, 95};

📝 Conclusion

Java fundamentals create the base required for learning advanced concepts like OOP, file handling, multithreading, exception handling, collections, and GUI frameworks. Understanding syntax, variables, operators, control flow, and input/output ensures a strong foundation for building Java applications of any complexity.