Get the last three chars from any string – Java

Why not just String substr = word.substring(word.length() - 3)?

Update

Please make sure you check that the String is at least 3 characters long before calling substring():

if (word.length() == 3) {
  return word;
} else if (word.length() > 3) {
  return word.substring(word.length() - 3);
} else {
  // whatever is appropriate in this case
  throw new IllegalArgumentException("word has fewer than 3 characters!");
}