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Mastering Kotlin Essentials

Introduction to Operator Overloading

Explore operator overloading in Kotlin to understand how to define special methods that allow using operators like + and - with custom classes. Learn to improve code readability by implementing operator functions with the operator modifier, applying these concepts to classes such as Complex numbers.

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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 ...