How to bind a value to an ObservableList's size?

Question

I want to bind a value to the ObservableList's size to know its size and also to know if it has multiple values

private ObservableList<String> strings = FXCollections.observableArrayList();

Answer 1

They can be bound with the Bindings class:

ObservableList<String> strings = FXCollections.observableArrayList();
IntegerBinding sizeProperty = Bindings.size(strings);
BooleanBinding multipleElemsProperty = new BooleanBinding() {
    @Override protected boolean computeValue() {
        return strings.size() > 1;
    }
};