Java - Count exactly 60 characters from a string with a mixture of UTF-8 and non UTF-8 characters

Question

I have a string which i want to save in a database that only supports UTF8 characters. If the string size is > 60 characters i want to truncate it and only store the first 60 characters. The Oracle database in use only supports UTF-8 characters.

Using String.substring(0,59) in Java returns 60 characters but when i save it in the database it gets rejected as the database claims that the string is > 60 characters.

• Is there a way to find out if a particular string contains non UTF8 characters. One option i found is:

  try {

      bytes = returnString.getBytes("UTF-8");
  
  
  } catch (UnsupportedEncodingException e) {
      // Do something
  

  }

• is there a way i can truncate it to exactly x number of characters (loss of data is not an issue) and make sure that when saved in the database only x number of characters are saved. For example if i have the string §8§8§8§8§8§8§8 and i say truncate and save only 5 characters it should only save §8§

Answer 1

As far as I understand you want to limit the String length in a way that the encoded UTF-8 representation does not exceed 60 bytes. You can do it this way:

String s=…;
CharsetEncoder enc=StandardCharsets.UTF_8.newEncoder();
ByteBuffer bb=ByteBuffer.allocate(60);// note the limit
CharBuffer cb = CharBuffer.wrap(s);
CoderResult r = enc.encode(cb, bb, true);
if(r.isOverflow()) {
    System.out.println(s+" is too long for "
                      +bb.capacity()+" "+enc.charset()+" bytes");
    s=cb.flip().toString();
    System.out.println("truncated to "+s);
}