Scala Cheat Sheet

Scala syntax, case classes, pattern matching, immutable collections, and functional programming features that run on the JVM.

2 PagesAdvancedApr 15, 2026

Basic Syntax

Values, variables, and control flow.

scala

val age = 30                  // immutable valuevar count = 0                  // mutable variableval name = "Ada"val pi: Double = 3.14159if (age >= 18) {  println(s"$name is an adult")}for (i <- 0 until 5) {  println(s"Count: $i")}

Case Classes & Pattern Matching

Idiomatic data modeling and dispatch.

scala

case class Point(x: Int, y: Int)val p = Point(1, 2)val p2 = p.copy(y = 5)         // immutable updatedef describe(x: Any): String = x match {  case 0 => "zero"  case n: Int if n > 0 => "positive"  case Point(0, 0) => "origin"  case Point(_, _) => "some point"  case _ => "unknown"}

Collections

Immutable, functional collection operations.

scala

val nums = List(5, 3, 1, 4, 2)val evens = nums.filter(_ % 2 == 0)     // List(4, 2)val squared = nums.map(n => n * n)      // List(25, 9, 1, 16, 4)val sum = nums.sum                       // 15val sorted = nums.sorted                 // List(1, 2, 3, 4, 5)val opt: Option[Int] = nums.find(_ > 10)  // None

Core Keywords

Common Scala language keywords.

val/var- immutable and mutable bindings (prefer val)
case class- immutable data class with structural equality and copy()
object- defines a singleton (used for companion objects, static-like members)
trait- reusable interface that can hold implementation, mixed in with 'with'
Option[T]- Some(value) or None instead of null
match- powerful pattern-matching expression
for (a <- xs) yield- for-comprehension producing a new collection
implicit- compiler-provided parameter or conversion (use sparingly)

Pro Tip

Prefer immutable `val` and persistent collections (List, Vector) over mutable ones — Scala's collections are optimized for structural sharing, so copies are cheap.

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