Scala Class and Objects

Scala Classes are a blueprint for creating objects. They can contain methods, values, variables, types, objects, traits, and Classes that are Collectively called Members.

Minimal Class Definition in Scala is simply the Keyword Class and an identifier.
Class Name should be capitalized.

Let’s take a look at an example of a class in Scala.

class Person
val person1 = new Person

In Scala, new a keyword is used to create an instance of the Class. Here Class Person has a default constructor which takes no arguments because we have not defined any constructor.

Let’s look at a more complex Example

//Defines a new MyClass with a Constructor
class NewClass(x:Int ,y: Int) { 
  require(y > 0, "y must be positive") //precondition triggering an IllegalArgument if not Met

  def nb1 = x               //public method which is computed every time it is called
  def nb2 = y
  private def test(a:Int):Int= { a} //Private Method
  val nb3 = x+y   //Computed Only Once

  override def toString =
    x+","+y
}
val newClass = new NewClass(2,2)
println(newClass.nb1)

Here toString method does not take arguments but returns a String Value.
As toString methods override the toString from AnyRef, it is used with override Keyword

Object Hierarchy in Scala

• scala.Any is the base type of all types. It has methods like hasCode  toString that can be overridden.
• scala.AnyVal is the base type of all primitive types. (scala. Double, scala. Float )
• scala.AnyRef is a base type of all reference types. (alias of java.lang.Object, supertype of java.lang.String , scala.List or any user-defined types)
• scala. Null is a subtype of any scala.AnyRef (null is the only instance of type Null) , and scala.Nothing is a subtype of any other type without any instance.

Companion Object in Scala

Scala does not have static methods or variables, but rather they have a singleton object or Companion object. Companion objects are compiled into classes that have static methods.

object HelloWorld {

def main(args:Array[String]){
println("Hello World")
}
}