Java Syntax & Structure – Java Fundamentals

Before diving into object-oriented programming or advanced features, it’s essential to understand Java’s basic syntax and program structure.

This foundation helps you read, write, and organize Java code properly.

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What is Java Syntax?

Syntax means the rules and structure that define how Java code must be written so the compiler can understand it.

Java syntax is strict but readable, inspired by C and C++.

Every Java program follows a clear, organized structure consisting of classes, methods, and statements.

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Basic Structure of a Java Program

Here’s a simple example:

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

Breakdown:

Part	Description
public class HelloWorld	Defines a class named HelloWorld. The file name must match this class name.
{ ... }	Curly braces define the body of a class or method.
public static void main(String[] args)	Entry point of every Java program — where execution starts.
System.out.println("Welcome to Java!");	Prints text to the console. Every statement ends with a semicolon ;.

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Key Syntax Rules

1. Case Sensitivity:

   Java is case-sensitive.

   → MyClass and myclass are different identifiers.

2. Class Names:

   Always start with an uppercase letter.

   Example: Student, BankAccount.

3. Method Names:

   Use camelCase convention.

   Example: calculateTotal(), getUserName().

4. File Name Rule:

   File name must match the public class name.

   → Class HelloWorld → File HelloWorld.java

5. Main Method Requirement:

   The main() method is mandatory to execute a Java program.

   public static void main(String[] args)
   

6. Statements End with Semicolons:

   Every executable statement ends with ;

7. Comments:

   Used for notes or documentation (ignored by compiler).

   // Single-line comment
   /* Multi-line
      comment */
   

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Common Elements of Java Programs

Element	Example	Description
Package Declaration	package myapp;	Organizes related classes
Import Statement	import java.util.*;	Includes built-in or external classes
Class Declaration	public class MyClass { }	Core building block of Java
Main Method	public static void main(String[] args)	Entry point
Statements	System.out.println("Hi");	Instructions to execute
Comments	// Example	Non-executable documentation

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Example: Program with Package & Import

package basics;

import java.util.Scanner;

public class InputExample {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter your name: ");
        String name = sc.nextLine();
        System.out.println("Hello, " + name + "!");
        sc.close();
    }
}

Here,

• package basics; → Groups the class inside a package named “basics”
• import java.util.Scanner; → Imports the Scanner class from Java’s library
• Scanner → Used to take input from the user

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Whitespace & Indentation

• Java ignores extra spaces, tabs, and newlines.
• But indentation makes your code more readable and professional.

Example (Good Practice ):

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

Example (Bad Practice ):

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

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Summary

Concept	Key Point
Case-sensitive	Keywords and identifiers must match case
Class structure	One public class per file
Main method	Execution starts from main()
Statements	Must end with ;
Comments	Used for notes, ignored by compiler
Indentation	Not mandatory but improves readability