Introduction to Scala

   This post gives you the basic introduction to the scala programming language

Topics I am covering in this post are

1. Classes
2. Traits
3. Objects
4. Packages

Classes : 

                Classes in Scala are very similar to classes in Java. They are templates containing fields and methods. Like in Java, classes can be instantiated using the new construct, there can be many “instances” (or “objects”) of the same class.

                In Scala there exists a special kind of class named case classes. You will learn about case classes during the course. 

                Classes in Scala cannot have static members. You can use objects (see below) to achieve similar functionalities as with static members in Java.

Traits : 

                Traits are like interfaces in Java, but they can also contain concrete members, i.e. method implementations or field definitions.

Objects : 

                Object in Scala are like classes, but for every object definition there is only one single instance. It is not possible to create instances of objects using new, instead you can just access the members (methods or fields) of an object using its name.

Packages : 

           Adding a statement such as package foo.bar at the top of a file makes the code in a file part of the package foo.bar. You can then do import foo.bar._ to make everything from package foo.bar available in your code. The content of a package can be scattered across many files. If you define a

class MyClass in package foo.bar, you can import that specific class (and not anything else from that package) with import foo.bar.MyClass.

           In Scala, everything can be imported, not only class names. So for instance if you have an object baz in package foo.bar,then import foo.bar.baz._ would import all the members of that object.

Sample Hello world program in scala  :

   Here I am writing the hello world program in two ways 

1 

object HelloWorld extends App

 { 

     println("Hello, World!")

}

2 

object HelloWorld {

      def main(args: Array[String]) {

      println("Hello, World!") }

}

         In Scala, the main or entry point method is defined in an object. An object can be made executable by either adding extending the type App or by adding a method defmain(args:Array[String]). 


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