Collections - [Array , List , Map, Set] / Filtering and Sorting

Array :-

fun main(args : Array<String>)

{

    var player = Array<String> (3){" "}  //initialization is necessary

    player[0]="Dhoni"

    player[1]="Sehwag"

    player[2]="Kohli"

//  player[9]="broad"  exception

    for(element in player)

    {

        println(element)

    }

    player[1]="KL Rahul"

    for(pl in 0..player.size-1)   //use of loop  Location wise

    {

        println(player[pl])

    }

    var num = Array<Int>(3){3}

    num[0]=55

    for(a in num)    //use of loop Directly

        println(a) 

}

List :-

fun main(args : Array<String>)

{

    var a = listOf<Int> (9,9,8)

    for(num in a)

    {

        println(num)

    }

//    for(num in 0..a.size-1)

    {

        println(a)

    }

   //  var b = mutableListOf<String>()

  //  var b = arrayListOf<Float>(5.9F, 6.7F,6.0F)

        var c = ArrayList<String> ()

        c.add("India")

        c.add("Pakistan")

        c.add("Isreal")

  //      c.remove("Pakistan")

   //     c.add(1,"Russia")

    c[1] = "Russia  n"

     for(element in c)

        println(element)

}

Map :-

fun main(args:Array<String>)

{

 //   var mymap =  mapOf<Int,String> ()

  // var abc = HashMap<Int,String> ()

  //  var abc = mutableMapOf<Int,String>()

    var abc = hashMapOf<Int,String>()

    abc.put(34,"cs")

    abc.put(12,"it")

    abc.put(89,"me")

    for(i in abc)

        println(i)

//    abc.put(12,"ko")

    abc.replace(12,"lm")

    for(key in abc.keys)

        println("Element at $key = ${abc[key]}")

}

Set :- 

contain unique value only no duplicates

fun main(args:Array<String>)

{

    var abc = hashSetOf<Int> (44,33,33,56,33,78,54,45)

    for(i in abc)

        println(i)

    var xyz = mutableSetOf<String>("aa","ab","cs","aa","aa","db","db")

    for (k in xyz)

        println(k)

    xyz.remove("db")

    xyz.add("kt")

    println("newc")

    for (k in xyz)

        println(k)

}

Filtering and Sorting :-

Filter and Map usage :-

Filter :-  filter our desired element out of collection.

Map :-  perform operation and modify elements.

eg :-

fun main(args : Array<String>)

{

    var mynum = listOf<Int>(2,3,4,8,66,55,99)

    var filt = mynum.filter { it<10 }   //filter usage  -- value less than 10

     for(i in filt)

      println(i)

    var mp = mynum.map { s -> s*s}  //map usage -- get new list square of previous one

     for(i in mp)

        println(i)

    println("both")

    var bth = mynum.filter { it<5 }.   //map and filter both usage 

                    map {it*it  }  //values less than 5 and square

    for(i in bth)

        println(i)

    println("In class")    //filter use in class created

    var per = listOf<person>(person("Lokesh",10),person("Vivek",14),person("Stranger",31),person("Lavish",19))

//    var myper =  per.filter {s->s.name.startsWith("L")}.map{it.name}

    var myper =  per.filter {it.age<20}.map{it.name}

    for(name in myper)

       println(name)

}

class person(var name:String, var age:Int)

{

    //some code

}

Predicates :-

'all' :-  Do all element satisfy the predicates/condition ?

'any' :-  Do any element satisfy the predicates/condition ?

'count' :- Total element that satisfy the predicates

'find' :- Return the First element that satisfy the Predicates

fun main(args:Array<String>)

{

    val numT = listOf<Int>(3,4,6,7,1,56,2,55,66,67,43,23)

    val fn = {s:Int -> s > 10}

    var check1 = numT.all(fn)    //output false  

    println(check1)

    var check2 = numT.any{s -> s>10}   //output true  

    println(check2)

    var count1:Int = numT.count{it>10}   //output 6 

    println(count1)

    var num1 = numT.find(fn)   //output 56 

    println(num1)

}