Hello World with some extra features in Scala

The ubiquitous "Hello World" program has been written in Scala to highlight some of the features of the language. A compiled scala programs runs on jvm. It can also import all the java classes as the example below shows.


//  _ the underscore is like wildcard to import all the classes of math package
import scala.math._
/**
 * @author Rajeev
 *
 */
// object keyword automatically created a singleton object for the class HelloWorld
object HelloWorld {

/*
just like java main is the starting point
we say 'obj : type' in scala rather than 'type obj' in java as type can be automatically inferred in many cases
def indicates it is a function
Unit indicates it is returning void
Array[String] means array of type string
without = sign in the definition it will become a procedure which returns nothing rather than a function
*/

  def main(args: Array[String]): Unit = {

// greet invoked like any method in java but it is passing a function, myFunc, in the arguments too
    println(HelloWorld.greet("Rajeev",myFunc))
     }
/* note that the parameter type => indicates it a by name function and wherever its name occurs in the current function it will be executed.
We don't neeed {} for single line function definitions
*/
  def greet (raj :String, afunc : => String) : String = "Hello World " + raj + " " + afunc + " " + math.Pi
  def myFunc =  "myfunc"
}

Apache Phoenix Installation

Apache Phoenix is the new kid on the block in HBase world http://phoenix.apache.org/ It provides a SQL layer on top of HBase and greatly improves productivity. It provides standard RDBMS create table statements and also the secondary indexes to be created. However, if HBase was a poor fit for the use case then Phoenix is not going to change the underlying reality.

Here are the instructions to install

This is how the final HBase architecture looks with Phoenix installed