is
Returns true if this character is permissible as the first character in a Java identifier.
Samples
import samples.*
import java.util.*
import kotlin.test.*
fun main() {
//sampleStart
val chars = listOf('a', '_', 'β', '$', '1', '+', ';')
val (javaIdentifierStarts, notJavaIdentifierStarts) = chars.partition { it.isJavaIdentifierStart() }
assertPrints(javaIdentifierStarts, "[a, _, β, $]")
assertPrints(notJavaIdentifierStarts, "[1, +, ;]")
//sampleEnd
}