Java中Collections.emptyList()的注意事项

public void run() {
  ......
  List list = buildList(param);
  ......
  Object newNode = getNode(...);
  list.add(newNode);
  ......
}
 
public List buildList(Object param) {
  if (isInValid(param)) {
    return Collections.emptyList();
  } else {
    ......
  }
}

public static final <T> List<T> emptyList() {
  return (List<T>) EMPTY_LIST;
}

public static final List EMPTY_LIST = new EmptyList<>();

private static class EmptyList<E>
    extends AbstractList<E>
    implements RandomAccess, Serializable {
    private static final long serialVersionUID = 8842843931221139166L;
 
    public Iterator<E> iterator() {
      return emptyIterator();
    }
    public ListIterator<E> listIterator() {
      return emptyListIterator();
    }
 
    public int size() {return 0;}
    public boolean isEmpty() {return true;}
 
    public boolean contains(Object obj) {return false;}
    public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
 
    public Object[] toArray() { return new Object[0]; }
 
    public <T> T[] toArray(T[] a) {
      if (a.length > 0)
        a[0] = null;
      return a;
    }
 
    public E get(int index) {
      throw new IndexOutOfBoundsException("Index: "+index);
    }
 
    public boolean equals(Object o) {
      return (o instanceof List) && ((List<?>)o).isEmpty();
    }
 
    public int hashCode() { return 1; }
 
    // Preserves singleton property
    private Object readResolve() {
      return EMPTY_LIST;
    }
  }

public boolean add(E e) {
  add(size(), e);
  return true;
}
 
public void add(int index, E element) {
  throw new UnsupportedOperationException();
}