public byte[] asUtf8() {
        if (utf8 == null) {
            utf8 = Utf8Codec.encode(value);
        }
        return utf8;
    }
A value holding a String in Java native format.
See also @ref Utf8Value (for lazy decoding).

@author havardpe
vespajlib/src/main/java/com/yahoo/slime/StringValue.java