Category : Scala | Sub Category : Scala Programs | By Runner Dev Last updated: 2020-10-08 14:26:54 Viewed : 226
Scala trait,extends,with and Unit
A trait is like an interface with a
partial implementation. In scala, trait is a collection of abstract and non-abstract
methods.
· Extends Keyword
We inherit
from can either be a trait or a class, using the extends keyword.
trait X
class Y
class B extends Y
·
with
keyword
We can define inherited traits (and only traits) using the with keyword.
class A extends Y with X
·
scala.Unit
Unit is a subtype of scala.AnyVal. There is only one value of type Unit, (), and it is not represented by any object in the
underlying runtime system. A method with return type Unit is analogous to a Java method which
is declared void
Way of declaring the traits and Unit:
trait Speaker {
def speak(): String // has no body, so it’s
abstract
}
trait TailWagger {
def startTail(): Unit = println("tail is
wagging")
def stopTail(): Unit = println("tail is
stopped")
}
trait Runner {
def startRunning(): Unit = println("I’m running")
def stopRunning(): Unit = println("Stopped
running")
}
Example:
Following
example illustrates about Scala for loop and Yield
Save
the file as − ScalaTraitEx.scala.
ScalaTraitEx.scala
package runnerdev
def disply()
}
class Test extends TestReader
{
def disply() {
println("called displayed method")
}
}
object ScalaTraitEx
{
def main(args: Array[String]) {
var test = new
Test()
test.disply()
}
}
compile
and run the above example as follows
scala> scalac ScalaTraitEx.scala
scala> scala ScalaTraitEx
called displayed method
Example 2:
Following
example illustrates about Scala for loop and Yield
Save
the file as − ScalaTraitEx2.scala.
ScalaTraitEx2.scala
package runnerdev
trait Speaker {
def speak(): String
// has no body, so it’s
abstract
def show() { //
Non-abstract method
println("This is show method")
}
}
trait TailWagger
{
def startTail(): Unit = println("tail is wagging")
def stopTail(): Unit = println("tail is stopped")
}
class TestOne extends Speaker with TailWagger
{
def disply() {
println("calling disply method")
}
def speak(): String
= {
return "calling speak method"
}
}
object ScalaTraitEx2 {
def main(args: Array[String]) {
var test = new
TestOne()
test.disply()
var str = test.speak()
println(str)
test.show()
test.startTail()
test.stopTail()
}
}
Output:
calling disply method
calling speak method
This is show method
tail is wagging
tail is stopped