error: type mismatch; found : scala.this.Unit required: scala.this.Int

Question

class Demo {

  def add (x:Int, y:Int): Int = {    
    val sum = x+y
    println(sum)   
  }  

}

val vvr = new Demo
vvr.add(1,2)

Answer 1

You defined the add function to return Int, but you're not returning anything.

Change to the following:

def add (x:Int, y:Int): Int = {
  val sum = x+y
  println(sum)
  sum
}

Now you can assign the result to a variable.

Alternatively, you can change Int to Unit in the function's definition.