[FIXED] What is the ObservableSet equivalent for setAll() method from ObservableList

Issue

What method should I use in the setter of a JavaFX ObservableSet collection to clear the set and initialise it to the given collection? ObservableList has the method setAll(Collection) that is used to initialise the list by first clearing it.

The closest I have seen is addAll(Collection) which does not clear the set beforehand. When setting the collection in my project I want it to have the normal behaviour of setting the ObservableSet to a new set, but according to the javadoc:

Adds all of the elements in the specified collection to this set if they're not already present (optional operation). If the specified collection is also a set, the addAll operation effectively modifies this set so that its value is the union of the two sets.

I cannot just set the value using = because the passed parameter in the setter is a set and the ObservableSet is an internal wrapper that the outside knows nothing about. I also would like to avoid doing clear then addAll.

Solution

As you can see in the Javadoc of ObservableSet, there is no such method.

In fact, the method ObservableList::setAll is just a convenient "shortcut":

Clears the ObservableList and add all elements from the collection.

The common implementation ModifiableObservableListBase in JavaFX does a clear then an addAll:

@Override
public boolean setAll(Collection<? extends E> col) {
    beginChange();
    try {
        clear();
        addAll(col);
    } finally {
        endChange();
    }
    return true;
}

The main advantage of having a setAll shortcut is that only one "big" change event (ListChangeListener.Change) is sent to the listeners. Better performance.

In fact, you might want to extend com.sun.javafx.collections.ObservableSetWrapper with your own setAll but there will be no performance benefit since the event SetChangeListener.Change is an elementary change: m removed events, and n added events will be sent.

So you have no other choice than:

set.clear();
set.addAll(otherSet);

or copy in a new set and assign:

set = FXCollections.observableSet(otherSet);

Answered By - gontard
Answer Checked By - Cary Denson (JavaFixing Admin)