private static boolean verifyFirst(byte c, byte [] identifier) {
        if (!((c == '_') || ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z')))) {
            throw new IllegalArgumentException("Illegal starting character '" + (char)c + "' of identifier '" + new Utf8String(new Utf8Array(identifier)).toString() +"'.");
        }
        return true;
    }
This class is used to represent a legal identifier of [a-zA-Z_][a-zA-Z_0-9]*

@author baldersheim
vespajlib/src/main/java/com/yahoo/text/Identifier.java