sclass CloseablesHolder extends Meta implements AutoCloseable, IResourceHolder {
  new LinkedHashSet<AutoCloseable> closeables;
  WeakRef<Thread> createdInThread = weakRef(currentThread());
  
  public synchronized <A extends AutoCloseable> A add(A a) {
    if (a != null)
      closeables.add(a);
    ret a;
  }
  
  // remove from list, don't close
  synchronized <A extends AutoCloseable> A remove aka takeOut(A a) {
    closeables.remove(a);
    ret a;
  }
  
  // close and remove
  synchronized <A extends AutoCloseable> A close(A a) {
    if (a == null) ret a;
    closeables.remove(a);
    main close(a);
    ret a;
  }
  
  public void close {
    for (AutoCloseable c : reversed(cloneAndClear(closeables)))
      main close(c);
  }
  
  public synchronized void forget aka clear() {
    closeables.clear();
  }
}