O'Reilly logo

Programming Kotlin by Stefan Bocutiu, Stephen Samuel

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Sets

A set is a collection that contains no duplicate items. This means you can't have i1 and i2 in the collection if i1==i2 (which translates to i1.equals(i2) == true). The same reasoning applies for a null reference - you can't have more than one null item stored in your set.

To create instances of sets, you can use any of the methods in the following code example:

 data class Book(val author: String, val title: String, val year: Int, val isbn: String) val intSet: Set<Int> = setOf(1, 21, 21, 2, 6, 3, 2) //1,21,2,6,3 println("Set of integers[${intSet.javaClass.canonicalName}]:$intSet") val hashSet: java.util.HashSet<Book> = hashSetOf( Book("Jules Verne", "Around the World in 80 Days Paperback", 2014, "978-1503215153"), Book("George R.R. Martin", ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required