Java Syntax & Structure

Java has strict rules (syntax) that must be followed. It is case-sensitive and uses curly braces {} to define blocks of code.

The Class Structure

Every line of code that runs in Java must be inside a class.

public class MyClassName {
    // Code goes here
}

[!IMPORTANT] The filename must exactly match the class name. If the class is MyClass, the file must be MyClass.java.

The main() Method

As seen before, this is where execution starts.

public static void main(String[] args) {
    // Execution starts here
}

Comments

Comments are ignored by the compiler. Use them to explain your code.

// This is a single-line comment

/*
 * This is a 
 * multi-line comment
 */

Identifiers & Naming Conventions

Identifiers are names for classes, variables, and methods.

• Classes: PascalCase (e.g., MyFirstClass)
• Methods: camelCase (e.g., calculateTotal)
• Variables: camelCase (e.g., userAge)
• Constants: UPPER_SNAKE_CASE (e.g., MAX_VALUE)

Interactive Example

Try modifying the code below to print your own name!

println vs print

• System.out.println(): Prints text and moves to a new line.
• System.out.print(): Prints text and stays on the same line.

Quiz

Next Steps

Now we have the structure down. Next, we'll learn about storing data using Variables.