iwantcoding.com
🔥 Daily 👥 Rooms 🏆 Top Log in Sign up

Strings

By · Reviewed & last updated · Part of Kotlin Tutorial

Kotlin strings are immutable. Interpolation uses \$name or \${expression}. Triple-quoted strings preserve everything literally — perfect for multi-line content.

String operations + multi-line + raw

EXAMPLE
val name = "Ada"
val age  = 36

// Interpolation
val greeting = "Hello, $name! You are $age."
val message  = "You scored ${score * 100 / max}%."

// Multi-line / raw — no escape interpretation
val body = """
    Dear $name,
      Welcome to Kotlin.
    --
    \n is literal here, not a newline.
""".trimIndent()

// Building
val csv = listOf("a", "b", "c").joinToString(separator = ",")
val many = buildString {
    appendLine("# Report")
    for ((k, v) in items) append("$k: $v\n")
}

// Common methods
"Hello, World".uppercase()
"  spaced  ".trim()
"camelCase".replace(Regex("[A-Z]")) { "_" + it.value.lowercase() }    // 'camel_case'
"comma,separated,values".split(",")
"42".toInt()              // throws if invalid
"42x".toIntOrNull()       // null if invalid

// Padding + indexing
"$age".padStart(4, '0')   // '0036'
name[0]                   // 'A'
name.first(); name.last()

Why it matters

toIntOrNull(), toDoubleOrNull(), etc., are the idiomatic safe parsers. Pair them with ?: for defaults: val n = s.toIntOrNull() ?: 0.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
val name = "Ada"
println("Hello, $name!")
println("""
multi
line
""".trimIndent())
Try it Yourself »

Discussion

Loading…