filterNotTo

Appends all characters not matching the given predicate to the given destination.

@IgnorableReturnValueinline fun <C : Appendable> CharSequence.filterNotTo(destination: C, predicate: (Char) -> Boolean): C(source)

val text = "Kotlin is great!"
val result = StringBuilder()

// Append all characters that are NOT a space to the StringBuilder
text.filterNotTo(result) { it == ' ' }

println(result.toString())   // prints: Kotlinisgreat!

Source