JavaFX CheckBoxTreeItem检测复选框处于选中或未选中状态

CheckBoxTreeItem<String> rootItem = new CheckBoxTreeItem<>("Root");
CheckBoxTreeItem<String> item1 = new CheckBoxTreeItem<>("Item 1");
CheckBoxTreeItem<String> item2 = new CheckBoxTreeItem<>("Item 2");

rootItem.getChildren().addAll(item1, item2);

item1.selectedProperty().addListener((observable, oldValue, newValue) -> {
    if (newValue) {
        System.out.println("Item 1 is selected");
    } else {
        System.out.println("Item 1 is not selected");
    }
});

item2.selectedProperty().addListener((observable, oldValue, newValue) -> {
    if (newValue) {
        System.out.println("Item 2 is selected");
    } else {
        System.out.println("Item 2 is not selected");
    }
});