Unit in Kotlin can be used as the return type of functions that do not return anything meaningful. The Unit type has only one possible value, which is the Unit object.

Examples:

  fun redundantA(): Unit {
      return Unit // redundant, 'Unit' is returned by default and matches the expected return type
  }

  fun requiredA(condition: Boolean): Any {
      if (condition) return "hello"
      return Unit // explicit 'Unit' is required since the expected type is 'Any'
  }

  fun redundantB(condition: Boolean): Any = if (condition) {
      fun ancillary(): Int = 1
      println("${ancillary()}")
      Unit // redundant since the last expression is already of type 'Unit'
  } else {
      println("else")
  }

  fun requiredB(condition: Boolean): Any = if (condition) {
      1024
      Unit // required, otherwise '1024' (Int) would be the return value
  } else {
      println("else")
  }