An abstract class in Scala can have constructor parameters as well as type parameters. An abstract class in Scala is fully interoperable with Java. In other words, it is possible to call them from Java code without any intermediate wrappers.

So, what is the difference between an abstract class and the traits in Scala? As you have seen, an abstract class can have constructor parameters, type parameters, and multiple parameters. However, a trait in Scala can have only type parameters. The following is a simple example of an abstract class:

abstract class Animal(animalName:String = "notset") {
  //Method with definition/return type
  def getAnimalAge
  //Method with no definition with String return type
  def getAnimalGender : String
  //Explicit way of saying that no implementation is present
  def getAnimalOrigin () : String {} 
  //Method with its functionality implemented
  //Need not be implemented by subclasses, can be overridden if required
  def getAnimalName : String = {
    animalName
  }
}

In order to extend this class by another one, we need to implement the unimplemented methods earlier getAnimalAge, getAnimalGender, and getAnimalOrigin. For getAnimalName, we can override it or not, since its implementation is already there.