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Mastering Kotlin Essentials

Introduction to Operator Overloading

Explore operator overloading and learn how to use custom operators in classes.

We'll cover the following...

In Kotlin, we can add an element to a list using the + operator. In the same way, we can add two strings together. We can check if a collection contains an element using the in operator. We can also add, subtract, or multiply elements of type BigDecimal, which is a JVM class that is used to represent possibly big numbers with unlimited precision.

Kotlin 1.5
import java.math.BigDecimal
fun main() {
    val list: List<String> = listOf("A", "B")
    val newList: List<String> = list + "C"
    println(newList) // [A, B, C]
    val str1: String = "AB"
    val str2: String = "CD"
    val str3: String = str1 + str2
    println(str3) // ABCD
    println("A" in list) // true
    println("C" in list) // false
    val money1: BigDecimal = BigDecimal("12.50")
    val money2: BigDecimal = BigDecimal("3.50")
    val money3: BigDecimal = money1 * money2
    println(money3) // 43.7500
}

Using operators between objects is possible thanks to the Kotlin feature called operator overloading, which allows special kinds of methods to be ...