Java Syntax, Structure and Identifiers

The Skeleton of a Java File

// package declaration (optional)
package demo;

// imports (optional)
import java.util.Scanner;

// class declaration
public class MyClass {
    // fields and methods live inside the class
    public static void main(String[] args) {
        System.out.println("Java structure");
    }
}

Naming Rules for Identifiers

Identifiers are the names you give to classes, methods, variables and packages.

• May contain letters, digits, underscore (_) and dollar sign ($).
• Must begin with a letter, underscore or dollar sign (never a digit).
• Are case sensitive: Total and total are different names.
• Cannot be a Java keyword such as class, if or int.

Naming Conventions

• Classes: PascalCase, e.g. BankAccount.
• Methods and variables: camelCase, e.g. getBalance, totalAmount.
• Constants: UPPER_SNAKE_CASE, e.g. MAX_RETRIES.
• Packages: lowercase, e.g. com.company.project.

Grammar Basics

• Statements end with a semicolon (;).
• Blocks of code are enclosed in curly braces { }.
• Whitespace does not separate statements; it is only for readability.
• Java is case sensitive: main is not the same as Main.

Key Points

• A Java file is organised as package, imports, then one or more classes.
• Follow naming conventions so your code is readable and idiomatic.
• Semicolons close statements; braces group blocks.