static Object shallowClone(Object o) {
  if (o == null)
    return o;
    
  if (o instanceof List)
    ret cloneList((List) o);

  if (o instanceof Map) {
    final Map m = o instanceof TreeMap ? new TreeMap() : new HashMap();
    m.putAll((Map) o);
    return m;
  }
  
  if (o instanceof String || o instanceof Number || o instanceof Boolean)
    return o;
    
  if (o instanceof Object[]) {
    Object[] l = (Object[]) o;
    ret l.clone();
  }
  
  // clone an arbitrary custom object

  // TODO: use Constructor object and setAccessible
  //print("Cloning custom: " + o);
  final Object clone = o.getClass().newInstance();
  Class c = o.getClass();
  while (c != Object.class) {
    Field[] fields = c.getDeclaredFields();
    for (final Field field : fields) {
      if ((field.getModifiers() & Modifier.STATIC) != 0)
        continue;
      field.setAccessible(true);
      final Object value = field.get(o);
      field.set(clone, value);
    }
    c = c.getSuperclass();
  }
  return clone;
}