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A Brief Introduction to Scala
@pranavek

● Scala is new generation JVM language
– It is intended to be compiled to Java bytecode
– The resulting executable runs on the JVM
● The name Scala is a portmanteau of "scalable" and
"language" (SCAlable LAnguage)
● James Strachan, the creator of Groovy, described
Scala as a possible successor to Java

Scala Vs Java
● Similar to Java compiler javac, Scala has a compiler
scalac, which compiles Scala code into byte code
● You can call Scala from Java and Java from Scala, it
offers seems less integration
● Major Java programming IDE like Eclipse, Netbeans
and InetelliJ supports Scala
● Both are OOP, Scala goes one steps further and also
supports functional programming paradigm

● Type inference
● Lazy evaluation
– lazy val images = getImages()
if(viewProfile){
showImages(images)
}
else if(editProfile){
showImages(images)
showEditor()
}
else{
//do something without loading images
}
● Scala treats any method as they are variables

object HelloWorld {
def main(args: Array[String]) {
println("Hello, world!")
}
}
●object declaration (Singleton object: class with single object)
–Declares both a class called HelloWorld and an instance of that
class, also called HelloWorld
The classic Hello, World! program

● Convenience and flexibility
var capital = Map("US" -> "Washington", "France" -> "Paris")
capital += ("Japan" -> "Tokyo")
println(capital("France"))
– The notation in this example is high-level, to
the point
– Not cluttered with extraneous semicolons or type
annotations.
– Scala gives you fine-grained control if you need it
val x = new HashMap[Int, String]((1,”Hello”))
val x: Map[Int, String] = new HashMap()

● Growing new types
- Eric Raymond - cathedral and bazaar as two
metaphors of software development
→ scala.BigInt
def factorial(x: BigInt): BigInt =
if (x == 0) 1 else x * factorial(x - 1)
– Now, if you call factorial(30) you would get:
265252859812191058636308480000000

→ java.math.BigInteger
import java.math.BigInteger
def factorial(x: BigInteger): BigInteger =
if (x == BigInteger.ZERO)
BigInteger.ONE
else
x.multiply(factorial(x.subtract(BigInteger.ONE)))
- Attempted to implement all of these abstractions at the
same time would simply become too big to be manageable
- Scala allows users to grow and adapt the language in the
directions they need by defining easy-to-use libraries that
feel like native language support

● Scala is compatible
– It allows you to add value to existing code
– Build on what you already have - because it was designed for
seamless interoperability with Java
– Run-time performance is usually on par with Java programs
– Can call Java methods, access Java fields, inherit from Java
classes, and implement Java interfaces.
– Re-uses many of the standard Java library types.
– str.toInt instead of Integer.parseInt(str)
Why Scala?

● Scala is concise
– // this is Java
class MyClass {
private int index;
private String name;
public MyClass(int index, String name) {
this.index = index;
this.name = name;
}
}
– //scala
class MyClass(index: Int, name: String)

● Scala is high-level
– // this is Java
boolean nameHasUpperCase = false;
for (int i = 0; i < name.length(); ++i) {
if (Character.isUpperCase(name.charAt(i))) {
nameHasUpperCase = true;
break;
}
}
– //scala
val nameHasUpperCase = name.exists(_.isUpperCase)

● Interaction with Java
import java.util.{Date, Locale}
import java.text.DateFormat
import java.text.DateFormat._
object FrenchDate {
def main(args: Array[String]) {
val now = new Date
val df = getDateInstance(LONG, Locale.FRANCE)
println(df format now)
}
}

import java.util.{Date, Locale}
import java.text.DateFormat._
val df = getDateInstance(LONG, Locale.FRANCE)
println(df format now)

● A Scala Tutorial for Java programmers [Michel
Schinz, Philipp Haller]
● http://javarevisited.blogspot.in/
● Programming in Scala [Martin Odersky, Lex Spoon,
Bill Venners]
● wikipedia.com
References

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