substring

Learn to take parts of a string with substring.

substring

To take a part of a String, use substring(startIndex, endIndex). startIndex is inclusive, endIndex is exclusive.

val s = "Kotlin"
println(s.substring(0, 3))  // Kot
println(s.substring(2, 5))  // tli

Indices start at 0. substring(0, 3) takes characters at 0, 1 and 2; that is the first three letters. The String's length is a safe endIndex.

A single-argument substring(startIndex) also exists; it takes from that index to the end.

Exercise Take the first and last three letters

Write a fun main(). Assign "Kotlin" to val lang. Print lang.substring(0, 3) for the first three letters and lang.substring(3, 6) for the last three on separate lines.

Show example solution

fun main() {
    val lang = "Kotlin"
    println(lang.substring(0, 3))
    println(lang.substring(3, 6))
}

substring with one argument

substring(startIndex) takes one argument and returns the part from that index to the end of the String.

val s = "Kotlin"
println(s.substring(3))  // lin

From index 3 to the end: lin. This is the same as substring(3, s.length) but shorter.

In the two-argument form, endIndex cannot be smaller than startIndex; otherwise IndexOutOfBoundsException is thrown.

Test yourself

Complete the substring call

val part = s.____(0, 3)

Show answer

val part = s.substring(0, 3)

What does "Kotlin".substring(2, 5) return?
- tli
- Kot
- tlin
- in
Show answer

tli — Indices 2, 3, 4 give tli.
Match the substring results

substring(0, 3) of "Kotlin"

Kot
substring(3) of "Kotlin"

lin
substring(2, 5) of "Kotlin"

tli
substring(0, 6) of "Kotlin"

Kotlin

Next lesson: split and replace

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