Scala

• Values cannot be re-assigned

• The type of a value can be omitted and inferred, or it can be explicitly stated:

  • val x: Int = 1 + 1

• Variables are like values, except you can re-assign them. You can define a variable with the var keyword.

Methods

Methods are defined with the def keyword.

def add(x: Int, y: Int): Int = x + y
println(add(1, 2)) // 3

A method can take multiple parameter lists:

def addThenMultiply(x: Int, y: Int)(multiplier: Int): Int = (x + y) * multiplier
println(addThenMultiply(1, 2)(3)) // 9

The last expression in the body is the method’s return value. (Scala does have a return keyword, but it is rarely used.

def getSquareString(input: Double): String = {
  val square = input * input
  square.toString
}
println(getSquareString(2.5)) // 6.25

Classes

class Greeter(prefix: String, suffix: String) {
  def greet(name: String): Unit =
    println(prefix + name + suffix)
}

The return type of the method greet is Unit, which signifies that there is nothing meaningful to return. It is used similarly to void in Java and C.