How to substring by bytes

Question

Hi,
I need to save strings in different langauges in the DB, up to 24 bytes.
How can i substring by bytes in java?
for example:
Èçðàèëü - is 14 bytes, but the string length is 7
hhhhhhh - is 7 bytes and the string length is 7.
i would like to cut it by bytes - up to 7 bytes.
if i use substring method, i get 14 bytes for the Russian letters!
how can i do it?
Thanks!

Answer 1

Find out what encoding your database uses.
Based on that, you can encode a character at a time to bytes (using String.valueOf(character).getBytes(encoding)) and count the bytes used.
When the required number of bytes are reached, return the string so far:
import java.nio.charset.Charset;
public class StringTrimToBytes {
        final Charset     charset;
        public StringTrimToBytes (String charsetName) {
                charset = Charset.forName(charsetName);
        public String trim (String string, int byteLength) {
                for (int index = 0, len = string.length(), bytes = 0; index < len; ++index) {
                        bytes += String.valueOf(string.charAt(index)).getBytes(charset).length;
                        if (bytes > byteLength)
                                return string.substring(0, index);
                return string;
        public static void main (String...args) {
                final StringTrimToBytes trimmer = new StringTrimToBytes("UTF-8");
                for (String arg : args)
                        System.out.println(trimmer.trim(arg, 5));
}But quite how you explain the behaviour to your users might be a bit tricky - "why can I put my address in if I don't spell the street name with an accent, but not otherwise?"