make hello world page language agnostic

Author: bishabosha

_overviews/scala3-book/taste-hello-world.md

@@ -7,18 +7,45 @@ previous-page: taste-intro
 next-page: taste-repl
 ---
 
+> **Hint**: in the following examples try picking your preferred Scala version.
+> <noscript><span style="font-weight: bold;">Info</span>: JavaScript is currently disabled, code tabs will still work, but preferences will not be remembered.</noscript>
+
 ## Your First Scala Program
 
-A Scala 3 “Hello, world!” example goes as follows.
+
+A Scala “Hello, World!” example goes as follows.
 First, put this code in a file named _hello.scala_:
 
+
+<!-- Display Hello World for each Scala Version -->
+{% tabs hello-world-demo class=tabs-scala-version %}
+
+{% tab 'Scala 2' for=hello-world-demo %}
+```scala
+object hello {
+  def main(args: Array[String]) = {
+    println("Hello, World!")
+  }
+}
+```
+> In this code, we defined a method named `main`, inside a Scala `object` named `hello`.
+> An `object` in Scala is similar to a `class`, but defines a singleton instance that you can pass around.
+> `main` takes an input parameter named `args` that must be typed as `Array[String]`, (ignore it for now).
+
+{% endtab %}
+
+{% tab 'Scala 3' for=hello-world-demo %}
 ```scala
-@main def hello() = println("Hello, world!")
+@main def hello() = println("Hello, World!")
 ```
+> In this code, `hello` is a method.
+> It’s defined with `def`, and declared to be a “main” method with the `@main` annotation.
+> It prints the `"Hello, World!"` string to standard output (STDOUT) using the `println` method.
+
+{% endtab %}
 
-In this code, `hello` is a method.
-It’s defined with `def`, and declared to be a “main” method with the `@main` annotation.
-It prints the `"Hello, world!"` string to standard output (STDOUT) using the `println` method.
+{% endtabs %}
+<!-- End tabs -->
 
 Next, compile the code with `scalac`:
 
@@ -28,6 +55,19 @@ $ scalac hello.scala
 
 If you’re coming to Scala from Java, `scalac` is just like `javac`, so that command creates several files:
 
+<!-- Display Hello World compiled outputs for each Scala Version -->
+{% tabs hello-world-outputs class=tabs-scala-version %}
+
+{% tab 'Scala 2' for=hello-world-outputs %}
+```bash
+$ ls -1
+hello$.class
+hello.class
+hello.scala
+```
+{% endtab %}
+
+{% tab 'Scala 3' for=hello-world-outputs %}
 ```bash
 $ ls -1
 hello$package$.class
@@ -37,14 +77,18 @@ hello.scala
 hello.class
 hello.tasty
 ```
+{% endtab %}
+
+{% endtabs %}
+<!-- End tabs -->
 
 Like Java, the _.class_ files are bytecode files, and they’re ready to run in the JVM.
 
 Now you can run the `hello` method with the `scala` command:
 
 ```bash
 $ scala hello
-Hello, world!
+Hello, World!
 ```
 
 Assuming that worked, congratulations, you just compiled and ran your first Scala application.
@@ -64,6 +108,27 @@ import scala.io.StdIn.readLine
 
 To demonstrate how this works, let’s create a little example. Put this source code in a file named _helloInteractive.scala_:
 
+<!-- Display interactive Hello World application for each Scala Version -->
+{% tabs hello-world-interactive class=tabs-scala-version %}
+
+{% tab 'Scala 2' for=hello-world-interactive %}
+```scala
+import scala.io.StdIn.readLine
+
+object helloInteractive {
+
+  def main(args: Array[String]) = {
+    println("Please enter your name:")
+    val name = readLine()
+
+    println("Hello, " + name + "!")
+  }
+
+}
+```
+{% endtab %}
+
+{% tab 'Scala 3' for=hello-world-interactive %}
 ```scala
 import scala.io.StdIn.readLine
 
@@ -73,6 +138,10 @@ import scala.io.StdIn.readLine
 
   println("Hello, " + name + "!")
 ```
+{% endtab %}
+
+{% endtabs %}
+<!-- End tabs -->
 
 In this code we save the result of `readLine` to a variable called `name`, we then
 use the `+` operator on strings to join `"Hello, "` with `name` and `"!"`, making one single string value.