Scala Basics

Java and Scala needs to be installed in VM

Using phython – streaming and machine learning having some issues

Scala is little bit tough

Installation of scala

Java -> sudo apt-get install openjdk-8-jdk

Java -> sudo apt-get install openjdk-7-jdk(Optional)

Scala -> www.scala-lang.org -> Download the latest One.

Go to Downloads -> tar -xvzf scala-file

sudo mv scala-2.11.7 /usr/local/scala

sudo nano .bashrc

export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64

export SCALA_HOME=/usr/local/scala

export PATH=$PATH:$SCALA_HOME/bin

source ~/.bashrc

if you want to practice in windows

you can do like below

http://www.scala-lang.org/

click download

scala-2.11.7

once this done

you can go to cmd promt

go to bin

type scala

you can get the REPL

java 1.8 and scala is similar ?

no this not similar some features they introudec that’s it

java 8 – is not funcational programming language

Scala – fully matured

Type inferences

Virtual extensive

Fully functional

Immutability

Conventional imperative language

Lamda collections – higher order functions (reuse and self-explanatory)

SCALA: Slogan writes less do more  

Immutability : you cant change at anytime

Scala is very faster than java

Java imitates scala play bean field

Some history :

1996: java 1.0                         1980’s – LISP& Machine learning

1997: PIZZA                             1999 -- HASKELL

1998: GJ                                  2001 -- Funnel

2000: java 1.3

2004: java 1.4

Incorporate both PIZZA came

2006 – they included all

Why scala in demand – its has Interactive Shell

Java don’t have the interactive shell

Evech and every line we cant debug and run in java

SCALA provides Interactive Shell

REPL  Stands

Read

Evaluate

Print

Loop

Read – compiles – results – loop

Most of the development will have in interactive shell

Variables:

Mutable – change

Immutable  -- constants

Scala only immutable data types

Mutalable – var

Immutable – val

Type inference – you no need to give this will let you know what its type

SCALA – scalable language

Default in scala is immutable

Def: define the funtions

PLAY : IDE for Spark – web based application by play

Expression,Variables,types,Functions

Variables

Functions

Expressions

Practice:

scala> "this is my text "

res16: String = "this is my text "

he re just I given single quotes it will print the same val duing the data type

variables:

scala> 'a'

res31: Char = a

scala> 1

res32: Int = 1

scala> 2.3

res33: Double = 2.3

scala> 2.5f

res34: Float = 2.5

scala> "Hello world"

res35: String = Hello world

if you want to see the all the commands which are using REPL you can type below

type  :

 scala> :

All commands can be abbreviated, e.g., :he instead of :help.

:edit <id>|<line>        edit history

:help [command]          print this summary or command-specific help

:history [num]           show the history (optional num is commands to show)

:h? <string>             search the history

:imports [name name ...] show import history, identifying sources of names

:implicits [-v]          show the implicits in scope

:javap <path|class>      disassemble a file or class name

:line <id>|<line>        place line(s) at the end of history

:load <path>             interpret lines in a file

:paste [-raw] [path]     enter paste mode or paste a file

:power                   enable power user mode

:quit                    exit the interpreter

:replay [options]        reset the repl and replay all previous commands

:require <path>          add a jar to the classpath

:reset [options]         reset the repl to its initial state, forgetting all session entries

:save <path>             save replayable session to a file

:sh <command line>       run a shell command (result is implicitly => List[String])

:settings <options>      update compiler options, if possible; see reset

:silent                  disable/enable automatic printing of results

:type [-v] <expr>        display the type of an expression without evaluating it

:kind [-v] <expr>        display the kind of expression's type

:warnings                show the suppressed warnings from the most recent line which had any

:line

:edit

:history

: reply

:t  : type of expression without evaluating

:t “hellp”

 This means “type of expression without evaluating “

scala> :t

:type [-v] <expression>

:t “dsdsd”

 scala> :help t

display the type of an express

scala> :t 3

Int

scala> :t 5+3

Int

scala> :t 'e'

Char

scala> :t "dsdsd"

String

scala> :t "dsdsdsd"+"dsdsd"

String

scala>

if you need any help related any command you can simply use the

:help t like this

scala> print("Hello World")

Hello World

scala> print(2)

2

scala> print(2+3)

5

scala> val x = 2 + 3

x: Int = 5

scala> print(x)

5

You can assing the value like

Val x = 30;

:t x  à you can find the type of the expression

You can give the type of val

Like

Val k:String=”siddu”

K

Scala Clear the screen:  Ctrl + L

BigINT:

You can declare as BigInt like below

scala> val i=BigInt("8498398438949834983984839443434343434")

i: scala.math.BigInt = 8498398438949834983984839443434343434

scala> i+1

res1: scala.math.BigInt = 8498398438949834983984839443434343435

BigDecimal:

scala> val i=BigDecimal("1.8498398438949834983984839443434343434")

i: scala.math.BigDecimal = 1.8498398438949834983984839443434343434

Defining methods:

Def  add(x:Double)= x+y

You can pass any value for these defined functions

Def add(x:Int):Double=x+y*x-10

You can mention the return type of the method as well

scala> def f2c (x : Double) : Double = (x-32)*5/9.0

f2c: (x: Double)Double

scala> def f2c (x : Double) : Int = (x-32)*5/9.0

<console>:11: error: type mismatch;

 found   : Double

 required: Int

       def f2c (x : Double) : Int = (x-32)*5/9.0

                                            ^

scala> def squareThenAdd ( x:Int,y:Int) = x*x + y*y

squareThenAdd: (x: Int, y: Int)Int

scala> def squareThenAdd ( x:Int,y:Int) :Double = x*x + y*y

squareThenAdd: (x: Int, y: Int)Double

scala> squareThenAdd(5,4)

res29: Double = 41.0

scala> def squareThenAdd ( x:Int,y:Int)  = x*x + y*y

squareThenAdd: (x: Int, y: Int)Int

scala> squareThenAdd(5,4)

res30: Int = 41

scala> def squareThenAdd ( x:Int)  = x*x + y*y

squareThenAdd: (x: Int)Int

Tuples and lists

Tuples and List are the data structures

You can store multiple lines working with group of elements

Val (int1, int2) = (2,4)

Val._1

Val._2

Val._3

Based on this you can retrieve

Scala> Val twoInts=(2,4)

scala> val twonts =(3,4)

twonts: (Int, Int) = (3,4)

scala> val twoStrings=("siddu","how are you")

twoStrings: (String, String) = (siddu,how are you)

scala> val threeDoubles=(1.2,1.3,4.5)

threeDoubles: (Double, Double, Double) = (1.2,1.3,4.5)

scala> val intAndString= (4,"siddu")

intAndString: (Int, String) = (4,siddu)

·         Tuples you can do max 22 not more than that.

Create List

Val list=List(3,4,5,6)

You can do all the list actions with in it

DROP:

You can drop the elements with in List

scala> val removeList=List(1,2,3,"naraismha","siddu")

removeList: List[Any] = List(1, 2, 3, naraismha, siddu)

scala> re

removeList   res1   res10   res11   res12   res13   res3   res4   res5   res6   res7   res9   ref   reflect

scala> re

<console>:11: error: not found: value re

       re

       ^

scala> removeList

res15: List[Any] = List(1, 2, 3, naraismha, siddu)

scala> val listAfterRemove=removeList.drop(2)

listAfterRemove: List[Any] = List(3, naraismha, siddu)

scala> listAfterRemove

res16: List[Any] = List(3, naraismha, siddu)

List examples more:

Defining list:

scala> val fruits=List("apple","mango","bananna","grapes")

fruits: List[String] = List(apple, mango, bananna, grapes)

scala> val digits=List(1,2,3,4,5,6,7)

digits: List[Int] = List(1, 2, 3, 4, 5, 6, 7)

scala> val empty=List()

empty: List[Nothing] = List()

scala> val mullists=List(

     | List(1,0,0),

     | List(0,1,0),

     | List(0,0,1)

     | )

mullists: List[List[Int]] = List(List(1, 0, 0), List(0, 1, 0), List(0, 0, 1))

List can have return type as well like below example

scala> val fruits:List[String]=List("apple","mango","bananna","grapes")

fruits: List[String] = List(apple, mango, bananna, grapes)

scala> val digits:List[Int]=List(1,2,3,4,5,6,7)

digits: List[Int] = List(1, 2, 3, 4, 5, 6, 7)

scala> val mullists:List[List[Int]]=List(

     | List(1,0,0),

     | List(0,1,0),

     | List(0,0,1)

     | )

mullists: List[List[Int]] = List(List(1, 0, 0), List(0, 1, 0), List(0, 0, 1))

scala> val empty:List[Nothing]=List()

empty: List[Nothing] = List()

scala> val empty:List[String]=List()

empty: List[String] = List()

Note: you can give either Nothing/String both can be accepts.

::

For using this you need to specify as ( left paranthis at any point of time )

scala> val fruits="apple"::("orange"::("pottato"::("grapes"::Nil)))

fruits: List[String] = List(apple, orange, pottato, grapes)

scala> val nums=1::(2::(3::(4::(5::Nil))))

nums: List[Int] = List(1, 2, 3, 4, 5)

For numbers you can do like below

scala> val numbers=1::2::3::4::Nil

numbers: List[Int] = List(1, 2, 3, 4)

you make a list like below one as well

scala> val xs=List("a")

xs: List[String] = List(a)

scala> val ys=List("b")

ys: List[String] = List(b)

scala> val zs=List("c")

zs: List[String] = List(c)

scala> val list1=xs:::ys:::zs

list1: List[String] = List(a, b, c)

scala> val list2=xs:::(ys:::zs)

list2: List[String] = List(a, b, c)

MKString:

scala> test.mkString("2");

res17: String = 122232425

here this will add to after 0 index and return type as String

Contains:

scala> test.contains(2)

res19: Boolean = true

Length:

scala> test.length

res20: Int = 5

Count:

scala> "hi how are you doing siddu".count(_=='a')

res0: Int = 1

scala> val myList=List(1,2,3,4,5,6,3,4,5,6,7)

myList: List[Int] = List(1, 2, 3, 4, 5, 6, 3, 4, 5, 6, 7)

scala> myList.count(_==4)

res1: Int = 2

addString:

scala> val str=new StringBuilder("hi")

str: StringBuilder = hi

scala> list.addString(str)

res27: StringBuilder = hi123

scala> list

res28: List[Int] = List(1, 2, 3)

scala> str

res29: StringBuilder = hi123

Map:

scala> val l = List(1,2,3,4)

l: List[Int] = List(1, 2, 3, 4)

scala> l.map(1+)

warning: there was one feature warning; re-run with -feature for details

res37: List[Int] = List(2, 3, 4, 5)

map can add 1 by one in each element

scala> l.map(1-)

warning: there was one feature warning; re-run with -feature for details

res40: List[Int] = List(0, -1, -2, -3)

if you subtrack

it will iterate as

1,2,3,4 – inside the list

1-1, 1-2,1-3,1-4

It will add/subtrack like this

If you want to import any package you have to do like below

scala> import scala.math.

BigDecimal      LowPriorityEquiv               Pi                           atan    expm1   min       sin         ulp

BigInt          LowPriorityOrderingImplicits   ScalaNumber                  atan2   floor   package   sinh

E               Numeric                        ScalaNumericAnyConversions   cbrt    hypot   pow       sqrt

Equiv           Ordered                        ScalaNumericConversions      ceil    log     random    tan

Fractional      Ordering                       abs                          cos     log10   rint      tanh

IEEEremainder   PartialOrdering                acos                         cosh    log1p   round     toDegrees

Integral        PartiallyOrdered               asin                         exp     max     signum    toRadians

scala> import scala.math._

import scala.math._

IF else condition

scala> def serveBeer(custAge:Int)=if(custAge>=22) println("take KF beer") else println("take water your not eligible")

serveBeer: (custAge: Int)Unit

scala> serveBeer(21)

take water your not eligible

scala> serveBeer(33)

take KF beer

scala>

Write a method and having some actions and action

Create a list and apply that list into using map

All the list values can be apply into particular function

scala> val people=List(22,33,44,55)

people: List[Int] = List(22, 33, 44, 55)

scala> people.map

map   mapConserve

scala> people.map(serveBeer)

take KF beer

take KF beer

take KF beer

take KF beer

res3: List[Unit] = List((), (), (), ())

scala>

here the return type is List you want to convert as String simply you can use as mkString like below

convert List type to string

scala> list.map(ServBeer).mkString(" ")

res7: String = please take water 11 please take KF beer please take KF beer please take KF beer

scala> list.map(ServBeer).mkString(" ,")

res8: String = please take water 11 ,please take KF beer ,please take KF beer ,please take KF beer

scala> list.map(ServBeer).mkString(",")

res9: String = please take water 11,please take KF beer,please take KF beer,please take KF beer

Filter in List

If you want to filter you can do like this but you can apply many things after returned list

scala> list.filter(20<)

warning: there was one feature warning; re-run with -feature for details

res12: List[Int] = List(22, 33, 44)

scala> list.filter(20<).map(ServBeer)

warning: there was one feature warning; re-run with -feature for details

res13: List[String] = List(please take KF beer, please take KF beer, please take KF beer)

scala> list.filter(20<).map(ServBeer).mkString(" ")

warning: there was one feature warning; re-run with -feature for details

res14: String = please take KF beer please take KF beer please take KF beer

scala> list.filter(20<).map(ServBeer).length

warning: there was one feature warning; re-run with -feature for details

res16: Int = 3

scala> list.length

res17: Int = 4

Retrieve the values from the list

scala> list(0)

res20: Int = 11

scala> list(1)

res21: Int = 22

scala> list(2)

res22: Int = 33

scala> val list:List[String]=List("cat","cow","elephent","deer")

list: List[String] = List(cat, cow, elephent, deer)

scala> list(0)

res31: String = cat

scala> def print(animal:String)=println(animal)

print: (animal: String)Unit

scala> list.map(print)

cat

cow

elephent

deer

res33: List[Unit] = List((), (), (), ())

forEach in List

scala> def mytest(passVal:Int)=println("hello this is int Val"+passVal)

mytest: (passVal: Int)Unit

scala> mytest(3)

hello this is int Val3

scala> customersList.for

forall   foreach

scala> customersList.foreach(mytest)

hello this is int Val11

hello this is int Val22

hello this is int Val33

hello this is int Val133

final defforeach(f: (A) ⇒ Unit): Unit

[use case]

Applies a function f to all elements of this list.

Note: this method underlies the implementation of most other bulk operations. Subclasses should re-implement this method if a more efficient implementation exists.

f

the function that is applied for its side-effect to every element. The result of function f is discarded.

Definition Classes

List → LinearSeqOptimized → IterableLike → GenericTraversableTemplate → TraversableLike → GenTraversableLike →TraversableOnce → GenTraversableOnce → FilterMonadic

Full Signature

final defforeach[U](f: (A) ⇒ U): Unit

scala> list.foreach(a=> println(a.length +"hello this is list of each element length"))

3hello this is list of each element length

3hello this is list of each element length

8hello this is list of each element length

4hello this is list of each element length

You can pass the argument as well

For Loop in list

for and yield

for while iterates  each  iteration have the values that would be store in buffer

in this loop its create and buffer and store that value

each type this going to save same type of the values for example

map – can map the map values

list having the list types..

examples

scala> for (i <- 1 to 5) yield i

res10: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 2, 3, 4, 5)

scala> for (i <- 1 to 10) yield i

res104: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

 scala> for (i<- 1 to 10) yield i*4

res115: scala.collection.immutable.IndexedSeq[Int] = Vector(4, 8, 12, 16, 20, 24, 28, 32, 36, 40)

scala> for(a <- list) println(a)

cat

cow

elephent

deer

scala> :t for(a<-list)

scala> :t for(a<-list) println(a)

Unit

scala> val nums=List(1,2,3)

nums: List[Int] = List(1, 2, 3)

scala> nums.m

map   mapConserve   max   maxBy   min   minBy   mkString

scala> nums.map(x=>x+1)

res117: List[Int] = List(2, 3, 4)

scala> nums.map(x=>x+1).map(x=>x*x)

res118: List[Int] = List(4, 9, 16)

Zip

scala> val names=List("narasimha","Anil", "hassan")

names: List[String] = List(narasimha, Anil, hassan)

scala> val sunames=List("bodagala","vasidreedy","nandamuri")

sunames: List[String] = List(bodagala, vasidreedy, nandamuri)

scala> names.zip(sunames)

res125: List[(String, String)] = List((narasimha,bodagala), (Anil,vasidreedy), (hassan,nandamuri))

Adding two lists

scala> names ++ sunames

res129: List[String] = List(narasimha, Anil, hassan, bodagala, vasidreedy, nandamuri)

scala> for((names,sunames) <- mixed) yield names + "\n"+ sunames

res133: List[String] =

List(narasimha

bodagala, Anil

vasidreedy, hassan

nandamuri)

scala> for((names,sunames) <- mixed) yield names + "/"+ sunames

res134: List[String] = List(narasimha/bodagala, Anil/vasidreedy, hassan/nandamuri)

scala> (for((names,sunames) <- mixed) yield names + "/"+ sunames).mkString("");

res135: String = narasimha/bodagalaAnil/vasidreedyhassan/nandamuri

scala> (for((names,sunames) <- mixed) yield names + " "+ sunames + " ").mkString("");

res145: String = "narasimha bodagala Anil vasidreedy hassan nandamuri "

scala> sentRaw.split(" ").toList.map(x=>x.split("/"))

res151: List[Array[String]] = List(Array(The, DT), Array(index, NN), Array(of, IN), Array(the, DT), Array(100, CD), Array(largest, JJS), Arra

rray(rose, VBD), Array(modestly, RB), Array(as, IN), Array(well, RB), Array(., .))

cate a mixed string and use some operations

scala> sentRaw.split(" ").toList.map(x=>x.split("/")).map(x=>Tuple2(x(0),x(1))

     | )

res185: List[(String, String)] = List((The,DT), (index,NN), (of,IN), (the,DT), (100,CD), (largest,JJS), (Nasdaq,NNP), (financial,JJ), (stocks,NNS), (rose,VBD), (modestly,RB), (as,IN), (well,RB), (.,.)

)

scala>

scala> val (a,b)=listpairs.unzip

a: List[String] = List(The, index, of, the, 100, largest, Nasdaq, financial, stocks, rose, modestly, as, well, .)

b: List[String] = List(DT, NN, IN, DT, CD, JJS, NNP, JJ, NNS, VBD, RB, IN, RB, .)

Regular Expressions:

Scala supports regular expressions through Regex class available in the scala.util.matching package

scala> val ambm="a+b+"

ambm: String = a+b+

scala> val ambm="a+b+".r

ambm: scala.util.matching.Regex = a+b+

in the above example you can observe one thing as .r (stands as regular expression)

scala> val worddigit1="\\w+\\dd+".r

worddigit1: scala.util.matching.Regex = \w+\dd+

scala> val WordDigit2 = """\\w+\\d+""".r

WordDigit2: scala.util.matching.Regex = \\w+\\d+

scala> val adder = "We're as similar as two dissimilar things in a pod.\n\t-Blackadder"

adder: String =

We're as similar as two dissimilar things in a pod.

                -Blackadder

scala> adder.split("\\s|")

res7: Array[String] = Array("", W, e, ', r, e, "", a, s, "", s, i, m, i, l, a, r, "", a, s, "", t, w, o, "", d, i, s, s, i, m, i, l, a, r, "", t, h, i, n, g, s, "", i, n, "", a, "", p, o, d, ., "", ""

, -, B, l, a, c, k, a, d, d, e, r)

scala> adder.split("\\s+")

res8: Array[String] = Array(We're, as, similar, as, two, dissimilar, things, in, a, pod., -Blackadder)

split with space

scala> val Name = """(Mr|Mrs|Ms)\. ([A-Z][a-z]+) ([A-Z][a-z]+)""".r

Name: scala.util.matching.Regex = (Mr|Mrs|Ms)\. ([A-Z][a-z]+) ([A-Z][a-z]+)

scala> val Name(title,firstname,lastname) = "Mr. Narasimharao Bodagala"

title: String = Mr

firstname: String = Narasimharao

lastname: String = Bodagala

Here once the match happens this will display as the names

scala> :t Name

scala.util.matching.Regex

Here you observe the name of the value type is “scala.util.matching.Regex”

scala> val Array(title,firsts,lasts) = "Mr. Narasimharao Bodagala".split(" ")

title: String = Mr.

firsts: String = Narasimharao

lasts: String = Bodagala

val Name = """(Mr|Mrs|Ms)\. ([A-Z][a-z]+) ([A-Z][a-z]+)""".r

Name: scala.util.matching.Regex = (Mr|Mrs|Ms)\. ([A-Z][a-z]+) ([A-Z][a-z]+)

scala> Name. click as tab after dot)

anchored       findAllIn        findFirstIn        findPrefixMatchOf   isInstanceOf   regex          replaceFirstIn   split      unanchored  

asInstanceOf   findAllMatchIn   findFirstMatchIn   findPrefixOf        pattern        replaceAllIn   replaceSomeIn    toString   unapplySeq  

scala> val smith="Mr. John Smith"

smith: String = Mr. John Smith

scala> val Name(title,fname,lname)=smith

title: String = Mr

fname: String = John

lname: String = Smith

scala> val matchesFound = Name.find

findAllIn   findAllMatchIn   findFirstIn   findFirstMatchIn   findPrefixMatchOf   findPrefixOf

scala> val matchesFound = Name.findAll

findAllIn   findAllMatchIn

scala> val matchesFound = Name.findAllIn(smith);

matchesFound: scala.util.matching.Regex.MatchIterator = non-empty iterator

scala> matchFound

res10: scala.util.matching.Regex.MatchIterator = non-empty iterator

scala> matchFound.fo

fold   foldLeft   foldRight   forall   foreach

scala> matchFound.foreach(print)

Mr. Jhon Smith

scala> val matchesFound = Name.findAllIn(smith).toList

matchesFound: List[String] = List(Mr. John Smith)

scala> matchesFound(0)

res2: String = Mr. John Smith

scala> val sentence = "Mr. John Smith said hello to Ms. Jane Hill and then to Mr. Ramesh Rao";

sentence: String = Mr. John Smith said hello to Ms. Jane Hill and then to Mr. Ramesh Rao

scala> val matchList=Name.findAllIn(sentence)

matchList: scala.util.matching.Regex.MatchIterator = non-empty iterator

scala> val matchList=Name.findAllIn(sentence).toList

matchList: List[String] = List(Mr. John Smith, Ms. Jane Hill, Mr. Ramesh Rao)

scala> matchList(0)

res14: String = Mr. John Smith

scala> matchList(1)

res15: String = Ms. Jane Hill

scala> matchList(2)

res16: String = Mr. Ramesh Rao

scala> val matchList=Name.findAllIn(sentence).matchData

matchList: Iterator[scala.util.matching.Regex.Match] = non-empty iterator

scala> val matchList=Name.findAllIn(sentence).matchData.toList

matchList: List[scala.util.matching.Regex.Match] = List(Mr. John Smith, Ms. Jane Hill, Mr. Ramesh Rao)

scala> val matchList=Name.findAllIn(sentence).matchData.toList.mkString("")

matchList: String = Mr. John SmithMs. Jane HillMr. Ramesh Rao

scala> val matchList=Name.findAllIn(sentence).matchData.toList.mkString(" ")

matchList: String = Mr. John Smith Ms. Jane Hill Mr. Ramesh Rao

Map,Contains,getOrElse,WithDefault,Keys and Values,groupBy,set,mapValues,keys and values,Option(Some and None),

scala>  val engToDeu = Map(("dog","Hund"),("cat","katze"),("rhinoceros","Nashorn"))

engToDeu: scala.collection.immutable.Map[String,String] = Map(dog -> Hund, cat -> katze, rhinoceros -> Nashorn)

So here dog – key

hund is value

key value pair as map

you can retrieve the value based on the key like below

scala> engToDeu("dog")

res20: String = Hund

scala> val engWord = List("dog","cat","rhinoceros");

engWord: List[String] = List(dog, cat, rhinoceros)

scala> val deuWords = List("Hund","katze","Nashorn")

deuWords: List[String] = List(Hund, katze, Nashorn)

scala> engWord.index

indexOf   indexOfSlice   indexWhere

scala> engWord.indexOf("cat");

res15: Int = 1

scala> deuWords(engWord.indexOf("cat"));

res16: String = katze

if you want add any elemnts into the list along with key and value like below

scala> engToDeu + "owl" -> "Eule";

res19: (String, String) = (Map(dog -> Hund, cat -> katze, rhinoceros -> Nashorn)owl,Eule)

Scala Objects:

Its like  data + functions called as objects

Class is nothing but blue print

Example:

object JohnSmith {

  val firstName = "John"

  val lastName = "Smith"

  val age = 37

  val occupation = "lingusist"

  def fullName: String = firstName + "   " + lastName

  def greet(formal: Boolean): String = {

   

    if(formal)

        "Hello my name is " +fullName+ "" + "and occupation: is" +occupation;

    else

       "Hello my name is " +firstName + ""+ lastName

  }

}

scala> JohnSmith.

age   asInstanceOf   firstName   fullName   greet   isInstanceOf   lastName   occupation   toString

you can find all the values here

you can access anything inside the objects using any data.

If you want to create another object you can do like the below

object JhonDow {

  val firstName = "John"

  val lastName = "Dow"

  val age = 24

  val occupation = "Computerscitist"

  def fullName: String = firstName + "   " + lastName

  def greet(formal: Boolean): String = {

    if (formal)

      "Hello my name is " + fullName + "" + "and occupation: is" + occupation;

    else

      "Hello my name is " + firstName + "" + lastName

  }

}

You come to know the differences more here

You can call for different

scala> JohnDow.firstName

res15: String = John

scala> JohnDow.lastName

res16: String = Dow

scala> John

JohnDow   JohnSmith

scala> JohnDow.fullName

res17: String = John   Dow

scala> JohnDow.greet(true)

res18: String = Hello my name is John   Dowand occupation: isComputerscitist

so all seems same except few values in this case how you can use here as

create two objects list and use

scala> val people=List(JohnDow,JohnSmith)

people: List[Object] = List(JohnDow$@598ec9af, JohnSmith$@722a20ec)

scala> people.map(person=>person.firstName)

<console>:14: error: value firstName is not a member of Object

       people.map(person=>person.firstName)

                                 ^

Here getting error because of this you have to create a class then create objects to call this.

Let me define the class now.

class person(

    val firstName: String,

    val lastName: String,

    val age: Int,

    val occupation: String) {

  def fullName: String = firstName + "   " + lastName

  def greet(formal: Boolean): String = {

    if (formal)

      "Hello my name is " + fullName + "" + "and occupation: is" + occupation;

    else

      "Hello my name is " + firstName + "" + lastName

  }

}

Once create the class you can see the magic

scala> val John

JohnDow   JohnSmith

scala> val j1 = new person("John","Smith",35,"lingusit")

j1: person = person@4ce10d40

scala> val j2 = new person("john","Dow",38,"scitist")

j2: person = person@190af581

scala> j1.

age   asInstanceOf   firstName   fullName   greet   isInstanceOf   lastName   occupation   toString

scala> j1.firstName

res24: String = John

so how easy you can create dynamics things instead of creating every time objects now you can create the list of elements of classes like persons

scala> val people=List(j1,j2,j3,j4)

people: List[person] = List(person@4ce10d40, person@190af581, person@2093decc, person@6c6cef3a)

see here

if you want to retrieve the values you can do the below like

scala> people.map(t=>t.firstName)

res34: List[String] = List(John, john, john, john)

scala> people.map(t=>t.age)

res37: List[Int] = List(35, 38, 48, 48)

scala> people.map(t=>t.age).sum

res38: Intscala> people.map(t=>t.age).sum/people.length

res42: Int = 42 = 169

scala> people.map(t=>t.age).sum/people.length.toDouble

res45: Double = 42.25

here list have different different objects

you can apply all the list operations for this .

scala> people.groupBy(t=>t.firstName)

res47: scala.collection.immutable.Map[String,List[person]] = Map(john -> List(person@190af581, person@2093decc, person@6c6cef3a), John -> List(

scala> people.groupBy(t=>t.firstName)("john").foreach(j=>println(j.greet(true)))

Hello my name is john   Dowand occupation: isscitist

Hello my name is john   pppmewand occupation: isdramist

Hello my name is john   mewand occupation: isdramist

Trait:

Its similar like interface in java

They renames as trait in scala that’s it

You can write a definations only nothing more than this required

scala> trait worker {

     |

     |   def workGreeting : String

     | }

Defined trait worker

scala> class Student(School:String,Subject:String) extends worker{

     |

     |   def workGreeting="I am Studying @"+ Subject + " @ " +  School;

     |

     | }

defined class Student

scala> val ts = new Student("ZPHS","Telugu")

ts: Student = Student@28bedd32

scala> ts.workGreeting

res61: String = I am Studying @Telugu @ ZPHS

scala> ts.School

<console>:14: error: value School is not a member of Student

       ts.School

          ^

Why here we cant access the School/subject so

Apply Functionality

scala> object addone {

     | def m1(x:Int)=x+2 }

defined object addone

scala> addone.m1(5)

res63: Int = 7

you can apply without calling of this

scala> object addone {

     | def apply(x:Int)=x+6 }

defined object addone

scala> addone(3)

res68: Int = 9