Scala2

// Good - Immutable case class
case class Person(name: String, age: Int)

// Bad - Mutable case class
case class Person(name: String, var age: Int)

// To change values, use copy constructor
val p1 = Person("Peter", 15)
val p2 = p1.copy(age = 16)

// Good - Immutable collections
val users = List(User("Alice", 30), User("Bob", 25))
val updatedUsers = users.map(u => u.copy(age = u.age + 1))

// Good - Pure function
def calculateTotal(items: List[Item]): BigDecimal =
  items.map(_.price).sum

// Bad - Impure function with side effects
def calculateTotal(items: List[Item]): BigDecimal = {
  println(s"Calculating total for ${items.size} items")  // Side effect
  val total = items.map(_.price).sum
  saveToDatabase(total)  // Side effect
  total
}

// Classes, traits, objects - PascalCase
class ClusterManager
trait Expression
object Configuration

// Packages - all lowercase ASCII
package com.databricks.resourcemanager

// Methods/functions - camelCase
def getUserById(id: Long): Option[User]
def processData(input: String): Result

// Constants - uppercase in companion object
object Configuration {
  val DEFAULT_PORT = 10000
  val MAX_RETRIES = 3
  val TIMEOUT_MS = 5000L
}

// Variables - camelCase, self-evident names
val serverPort = 1000
val clientPort = 2000
val maxRetryAttempts = 3

// One-character names OK in small, localized scope
for (i <- 0 until 10) {
  // ...
}

// Do NOT use "l" (Larry) - looks like "1", "|", "I"

// Enumeration object - PascalCase
// Values - UPPER_CASE with underscores
private object ParseState extends Enumeration {
  type ParseState = Value

  val PREFIX,
      TRIM_BEFORE_SIGN,
      SIGN,
      VALUE,
      UNIT_BEGIN,
      UNIT_END = Value
}

// Limit lines to 100 characters
// One space before and after operators
def add(int1: Int, int2: Int): Int = int1 + int2

// One space after commas
val list = List("a", "b", "c")

// One space after colons
def getConf(key: String, defaultValue: String): String = {
  // code
}

// Use 2-space indentation
if (true) {
  println("Wow!")
}

// 4-space indentation for long parameter lists
def newAPIHadoopFile[K, V, F <: NewInputFormat[K, V]](
    path: String,
    fClass: Class[F],
    kClass: Class[K],
    vClass: Class[V],
    conf: Configuration = hadoopConfiguration): RDD[(K, V)] = {
  // method body
}

// Class with long parameters
class Foo(
    val param1: String,  // 4 space indent
    val param2: String,
    val param3: Array[Byte])
  extends FooInterface  // 2 space indent
  with Logging {

  def firstMethod(): Unit = { ... }  // blank line above
}

// Always use curly braces for multi-line blocks
if (true) {
  println("Wow!")
}

// Exception: one-line ternary (side-effect free)
val result = if (condition) value1 else value2

// Always use braces for try-catch
try {
  foo()
} catch {
  case e: Exception => handle(e)
}

// Use uppercase L for long literals
val longValue = 5432L  // Do this