Saturday, April 11, 2009

Learning Scala 1 : A Hello World

Scala is a powerful and interesting language to learn. Personally, I like it as the next generation of my daily written Java programming language.

To getting started with Scala is easy. Get a Scala distribution from and unzip it to, for say C:\ and set C:\scala-2.7.3\bin into your PATH environment variable. It requires Java runtime environment version 1.5 or later installed on your machine, I am having Sun JDK 6 Update 13 installed on my Windows XP machine.

After the above setup, you can start Scala Interpreter by entering 'scala' in command prompt:-


Alternatively, you can start the Scala Interpreter also by double clicking 'scala.bat' under the 'bin' folder. You should after the Scala Interpreter waiting for your command now:-


Now, let's type 3 + 5 into it:-

scala> 3 + 5
res0: Int = 8

The 'res0' is a generated name to refer to the calculated value. You can try to print it out by using println():-

scala> println(res0)

You can declare 'val' (value) or 'var' (variable) in Scala, 'val' works similar like 'final' in Java, which reassignment is not allowed. You can try reassign the 'res0' to something else and you should get an error:-

scala> res0 = 9
:5: error: reassignment to val
res0 = 9

Now, let's declare a value call 'myValue':-

scala> val myValue = "Hello World"
myValue: java.lang.String = Hello World

You can see that I do not declare any type for myValue, the Scala compiler is smart enough to infer the value type to String, optionally, you can write it in the following way:-

val myValue:String = "Hello World"

Now, let's print it out:-

scala> println(myValue)
Hello World

That's complete my 'Hello World' in Scala!. ;-)