Options
Scala Option[ T ] is a
container for zero or one element of a given type. An Option[T] can be either Some[T] or None object, which
represents a missing value. For instance, the get method of Scala's Map
produces Some(value) if a value corresponding to a given key has been found, or None if the given
key is not defined in the Map.
Example :
object OptionsVar {
def main(args: Array[String]) {
val islands = Map("France" ->
"Europe", "Japan" -> "Asia")
println("show(islands.get(
\"Japan\")) : " + show(islands.get( "Japan")) )
println("show(islands.get(
\"India\")) : " + show(islands.get( "India")) )
}
def show(x: Option[String]) = x match {
case Some(s) => s
case None => "?"
}
}
//Output
show(islands.get(
"Japan")) : Asia
show(islands.get(
"India")) : ?
Using
getOrElse() Method
Following is the example program to show how
to use getOrElse() method to access a value or a default when no value is
present.
Example:
object Test {
def main(args:
Array[String]) {
val
a:Option[Int] = Some(3)
val
b:Option[Int] = None
println("a.getOrElse(0): " + a.getOrElse(0) )
println("b.getOrElse(10): " + b.getOrElse(9) )
}
}
//Output
a.getOrElse(0): 3
b.getOrElse(9): 9
Using
isEmpty() Method
Following is the example program to show how to use
isEmpty() method to check if the option is None or not.
Example
object Test {
def main(args:
Array[String]) {
val
a:Option[Int] = Some(1)
val
b:Option[Int] = None
println("a.isEmpty: " + a.isEmpty )
println("b.isEmpty: " + b.isEmpty )
}
}
//Output
a.isEmpty: false
b.isEmpty: true
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