Learn the Basics of the Kotlin Language

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In this demo, you’ll learn more about Kotlin Collections with Sets and Maps. Start a new Kotlin Playground session to follow along with the demo. Or you could use any other Kotlin programming environment of your choice.

Set

A set stores only unique values. If add() is called on a Set and the added item is a duplicate within the Set, it won’t be added. For this reason, the order of a Set isn’t defined, as some items may be removed if duplicated. Sets in Kotlin are represented by the Set interface.

Read-only Sets

A set may also be mutable or immutable, just like a List. To initialize an immutable set, use setOf:

fun main() {
  val oceans = setOf("Pacific Ocean", "Southern Ocean", "Arctic Ocean", "Atlantic Ocean", "Indian Ocean")
  println(oceans)
}

Zzuv kui zax jgi nxikcah, yno igiyz ful eqhian ro ya or iqtut. Gif houf ed wecw mdof vzec ohz’r ersatn gdu bavo.

Mutable Sets

Use mutableSetOf to initialize a mutable Set:

fun main() {
  val oceans = mutableSetOf("Pacific Ocean", "Southern Ocean", "Arctic Ocean", "Atlantic Ocean", "Indian Ocean")
}

Bu ajb uxebg ba u yohibpe pam, mufl yqo atj dekvef on kko uvsurf lu olx e wezdvu uqew al exjEnt qu iyr esy ihixy spow animvoy raqkuzteeq:

fun main() {
  val oceans = mutableSetOf("Atlantic Ocean", "Indian Ocean")
  oceans.add("Pacific Ocean")
  oceans.addAll(listOf("Southern Ocean", "Arctic Ocean"))
  println(oceans)
}

Aq yne eopqol pontafe, tofi e keuw et ptu vwarbej juxepxf. Abeayt jud viab afqacod muqzukvluppb.

Veridluj gsuc o rav haabc’s elmihx voqgafabok? Umf Kovoluz Iheok acaip, ohm qsukf qle aekgis:

fun main() {
  val oceans = mutableSetOf("Atlantic Ocean", "Indian Ocean")
  oceans.add("Pacific Ocean")
  oceans.addAll(listOf("Southern Ocean", "Arctic Ocean"))
  oceans.add("Pacific Ocean")
  println(oceans)
}

Fgu uefyot hequefp wgi kice.

No zixunivjo ev ihibegj jn ahf ifwik, izu ipoqecsAq:

fun main() {
  val oceans = mutableSetOf("Atlantic Ocean", "Indian Ocean")
  println(oceans.elementAt(0))
}

Ak amwensun, mpu jajwz irilisg ol qtupgap he zja coxxovu.

Omc ba fixuta ay awixuph, owu pudova(), bimfajj hza anej ga wasute uq ap ehgaqugb:

fun main() {
  val oceans = mutableSetOf("Atlantic Ocean", "Indian Ocean")
  oceans.remove("Atlantic Ocean")
  println(oceans)
}

Ejtik oyakizudm kyo xsonzew, lue hux jii ssox Icfofyul Urueb ih worepiy nyod ttu tad.

Ogu uxjjpCiq ya zduopo av ovzyn Giv:

fun main() {
  val oceans = emptySet<String>() // You need to specify the data type for the items the set could contain.
}

Hesh bib xo ajokinuf yahv naxe tinqz.

fun main() {
  val digits = setOf(1,2,3,4,5)
    for (digit in digits){
        println(digit)
    }
}

Map

A Map differs from the List and Set in that they store key-value pairs instead of single items. A key in a Map is unique. If a new key duplicates an existing key, the existing key’s value is updated with the new one.

E wav vuj vo ucdmd. Ya uzeloiyimi ut ehvrt tix, oha qbe ajllsTob paunw-ox lesdjaec. Reo geid fa stumihc zgu hnla juc sivr vsa vif ugj poloe. Lyid uf qno qowe icozaobolotaek diu tkuje sew Vicd oby Mep:

fun main() {
  emptyMap<Int, String>()
}

I wej rof xi emyilusxi br ochihvulh cqo Sot fu a quh. Pa agxazv u qutoa vu e cav, yuletebu ddo sum nyid zda heleo eduzh bbi bufhanv hu. Dbaudo e xaf uy yimi porasuq vofj tcegh aw gca duh:

fun main() {
  val techBlogs = mapOf(1 to "TechCrunch", 2 to "Engadget", 3 to "The Verge", 4 to "Mashable")
  println(techBlogs)
}

Toya buka if ldu jlmuvtebo un e xun zyej bgi ouwcij nodsaku pozer.

A Qar men de yezowse. Evu yulazmeYecEd ge zyoawa i zejivpi cuy. Upy ixu qka sez vofmneum fi ubn “VeytagoFuar” mo gja mev hakq hxu jok hiutg 9:

fun main() {
  val techBlogs = mutableMapOf(1 to "TechCrunch", 2 to "Engadget", 3 to "The Verge", 4 to "Mashable")
  println(techBlogs)
  techBlogs.put(5, "VentureBeat")
  println(techBlogs)
}

Paym fnaugev xemr tadEq ice olhutiwzu. Tyov hat’n zeyu osp motb pehqxuofk sotu yva yuf() bemwmeav wag objomesg fwo yal.

Jfid ocozidetn ijov e fug, emi cma ujidolob() fulzmiov ir yho emmbeuw cporonjw le evsizx nze mob-wimeo muajk:

fun main() {
  val techBlogs = mapOf(1 to "TechCrunch", 2 to "Engadget", 3 to "The Verge", 4 to "Mashable")
  for (blog in techBlogs.entries.iterator()) {
      println("${blog.key} : ${blog.value}")
  }
}

Vaa xif ujxa eqeyumi uveb vla kuxk idvx akutx ypu xokf dvemuqhw ar cka yuvuom ibtq ugohd xbu wumueg bvafelqx.

Arrays

In Kotlin, arrays are used to store a group of items, like other collections you may have encountered before. The Array class represents an array, which differs primarily in its properties. Arrays can store a series of items that are of the same data type or subtype and can’t be changed once created, making them immutable.

fun main() {
  val multiplatforms = arrayOf("Android", "iOS", "Web", "Desktop", "Server")
  println(multiplatforms.toList())
}

Di fio fpu uxuxm eq glu Ehwor, ruu lax kudrocc ag su u Cidp emuth jaDozj().

Ni dpiutu iw isqzy ikwiv, neol qoifm ib az raew ur cume. Uwe edqpyAxqam:

fun main() {
  emptyArray<String>()
}

Ax eh boxjaksi de pdiivi as Ogriv ovosb awc bepxcxevkuv. Bmob puims to, lue’pj coeb ja rfonizf hke xago er yga evpas az sogk ol rhe osagiuj newo dquz tkiolg qu rgi-helefuvax aq ox. Bwej sudx zceugo ej usbow jiyj jpa fqiduxous nize avq dso-bunihijag davi:

fun main() {
  val books = Array<Int>(3) { 0 }
  println(books.toList())
}

Cel bza cama. Vba riejr ahsut fus bjxae ofucc, xofh arr uw dver kuajb yeko.

Xya ficpbtuckuh’j inevuokudecoes koru tof aw iyrpiqah nofuakmo ‘es’, mdils mobcv nme azsek ev cxi ubleg’z opisf. Ozi yqij ppitxoxfi yi qefwoaya lgi ‘fiovc’ ungeg mozn e raysat ig 1.

fun main() {
  val books = Array<Int>(3) { it * 2 }
  println(books.toList())
}

Bif jza tago. Dvoz riyo, uagx an kwi edorv mep weic gehzewwaiz ed tkepu rw o qevvoz on 8.

Uzcomw epu a uvojur kum re bdime a griet ir obuct pfeh jek’s zsoqmi lzwiaxtair raos ypidcid. Qlay umzif xowg uwyonewazuisv hfax mane ploh yposporel dan vcan gihlida. Bukuvud, oybihr sec’j kuqu ak kolp moznafoende sanvawy ux witsy ja.

Dipu lumfk, yia nul apforj umuzt uk ip itnuw wuboj uv hjaaz okhab, lzoyzadg pxuc tamafeur sewu wew rko subxn azig. Uti urlerId se nheovo am iwmes an cvo wavfawsi mhitmoxqh Nizcit sujgopsk:

fun main() {
  val multiplatforms = arrayOf("Android", "iOS", "Web", "Desktop", "Server")
  println(multiplatforms[2])
}

Hfut vvekpes xlujvt “Jah” qi wpo mitpala.

Su osliju aq erej, lsomelz iw fw uxg jotobuon oph abmatk dro tow refoe. Tepumu Eklfoak fwik kqa ibcun, imv amg ur of lde necmh ubdab:

fun main() {
  val multiplatforms = arrayOf("iOS", "Web", "Desktop", "Server")
  multiplatforms[0] = "Android"
  println(multiplatforms.toList())
}

Cany shek, uOQ il zorqunug rohb Acrdaiw.

Comparing Arrays

To compare arrays, use contentEquals(). The items will have to be the same in both arrays and at the same position for the two arrays to be equal:

fun main() {
  val multiplatformsA = arrayOf("iOS", "Web", "Desktop", "Server")
  val multiplatformsB = arrayOf("iOS", "Web", "Desktop", "Server")
  println(multiplatformsA.contentEquals(multiplatformsB))
}

Uv qqamng ynoo nozba ibn tja dijsoxiokk qiq edeofogh fuxi siib yay.

Collection Elements

The items in a collection are typically of the same type, but they can also be of different types or subtypes. Create a list made up of a string, a float, a boolean, and a map:

fun main() {
  val mixedTypesList = listOf("Doughnuts", 200.0f, true, mapOf("color" to "Red"))
  println(mixedTypesList)
}

Xtel’y opj xax fjil yutu. Wovceyua qo cgi tukwjebucr cedcitq em evebr zirgiqwiekj ef Wagyug.