ObservableSetSize

An ObservableInt whose value is the size of an ObservableSet.

As example of where this might be useful. Suppose we want to disable a button when a set is empty. Simply bind its disabledProperty to :

ObservableSetSize(mySet).equalTo(0)

Alternatively, we might want a label to contain a list's size, in which case, bind its textProperty to :

ObservableSetSize(mySet).toObservableString()