Strings

String templates

Embed values directly in a string with $:

val name = "Kotlin"
val version = 2.0
println("Hello, $name!")              // simple variable
println("Version is ${version + 0.1}") // any expression in ${...}

Use ${...} for expressions; bare $name works for a simple variable.

Escapes and special characters

val tabbed = "name:\tKotlin"
val quote = "She said \"hi\""
val path = "C:\\temp"
val dollar = "\$5.00"   // a literal dollar sign

Multiline (raw) strings

Triple-quoted strings span lines and ignore escaping:

val json = """
    {
        "name": "Kotlin",
        "year": 2016
    }
""".trimIndent()

trimIndent() removes the common leading whitespace. trimMargin() trims up to a margin prefix (| by default).

Common operations

val s = "Kotlin"
s.length            // 6
s[0]                // 'K'  (indexing)
s.uppercase()       // "KOTLIN"
s.lowercase()       // "kotlin"
s.substring(0, 3)   // "Kot"
s.startsWith("Ko")  // true
s.contains("tli")   // true
s.replace("t", "T") // "KoTlin"
"a,b,c".split(",")  // ["a", "b", "c"]
"  hi  ".trim()     // "hi"

Equality

Use == for value equality (it calls .equals()), and === for reference identity:

val a = "hi"
val b = "h" + "i"
println(a == b)    // true  (same content)
println(a === b)   // may be false (different objects)

In Kotlin, == does what you usually want (content comparison). This is unlike Java, where == compares references for objects.

Exercises

Given val first = "Ada" and val last = "Lovelace", build the string "Lovelace, Ada" using a template.
Write initials(fullName: String): String that returns the uppercased first letter of each space-separated word. For "ada lovelace" it returns "AL".

Solution

   fun initials(fullName: String): String =
       fullName.split(" ")
           .filter { it.isNotEmpty() }
           .map { it.first().uppercaseChar() }
           .joinToString("")

</details>

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