public class Test {

  public static void main(String[] args) {
// split a string at every third character..
    String test = "12345678";
    // iterate through string..
    for (int i = 0; i < test.length(); i += 3) {
      if (i + 3 > test.length()) // near the end?
      {
        System.out.println(test.substring(i));
      } else // not near the end
      {
        System.out.println(test.substring(i, i + 3));
      }
    }
  }
}