Comments and Style

Comments

// A single-line comment
val taxRate = 0.2 // after code

/* A block comment
   spanning several lines */

/** A Scaladoc comment documents the definition below it.
  *
  * @param price the net price
  * @return the price including tax
  */
def withTax(price: Double): Double = price * (1 + taxRate)

@main def comments(): Unit =
  println(withTax(100))

120.0

Scaladoc comments (/** ... */) appear when you hover over a name in your editor, and scaladoc turns them into an HTML API reference.

Style guidelines

The official Scala style guide recommends:

• camelCase for values and methods, PascalCase for classes, traits, objects, and enums.
• Two-space indentation.
• val over var, immutable collections over mutable ones.
• Explicit return types on public methods.
• Short, expressive names in small scopes (n, x), descriptive names in larger ones (activeUsers).
• Methods without parameters that have no side effects are written without parentheses (list.size); methods with side effects keep them (reset()).

Tools

• scalafmt formats code automatically (scala fmt .).
• Scalafix and the compiler's warnings (-Wunused:all) find unused imports and other problems.

What's next

You now know the core of Scala. Try the Beginner Projects, then continue to Level 2 — Intermediate, which starts with classes and case classes.