Array List with If Condition [duplicate]

I have problem with creating arraylist.

1. Array list is created from splitted String "gh2".
2. Idea of program is to create array which will containt only characteristic String.
3. After creating Array, by string builder "sb2" I'm trying to create another splitted string,WYNIKI
4. When I'm calling back second value from WYNIKI, im gettin gerror about boundexpection...

ArrayList<String> listawynikow = new ArrayList<String>(gh2.length);
for (int i = 0; i < gh2.length; i++) {
  if (gh2[i].matches("[0-9]+")) {
    listawynikow.add(gh2[i]);
  }
}

StringBuilder sb2 = new StringBuilder();
for (int j = 0; j < listawynikow.size(); j++) {
  sb2.append(listawynikow.get(j)).append(";").append("\n");
}
String wyniki1 = sb2.toString();
String[] WYNIKI = wyniki1.split(";");

When I'm giving different if condition like for example negation of (!gh2[is].matches) everything is working good. Size of array is 23. When I'm checking String before splitting everything looks proper, and array is not empty.