1  import javafx.beans.InvalidationListener;
  2  import javafx.beans.Observable;
  3  import javafx.beans.property.DoubleProperty;
  4  import javafx.beans.property.SimpleDoubleProperty;
  5  
  6  public class ObservablePropertyDemo {
  7    public static void main(String[] args) {
  8      DoubleProperty balance = new SimpleDoubleProperty();
  9      balance.addListener(new InvalidationListener() {
 10        public void invalidated(Observable ov) {
 11          System.out.println("The new value is " + 
 12            balance.doubleValue());
 13        }
 14      });
 15  
 16      balance.set(4.5);
 17    }
 18  }