JavaFX DoubleProperty create from SimpleDoubleProperty

import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleDoubleProperty;

public class Main {
  public static void main(String[] args) {       
    DoubleProperty d1 = new SimpleDoubleProperty(1);
    DoubleProperty d2 = new SimpleDoubleProperty(2);
    d1.bind(d2);/*w w w  . j av a2  s  .  c  o m*/
    System.out.println("d1 is " + d1.getValue() + " and d2 is " + d2.getValue());
    d2.setValue(70.2);
    System.out.println("d1 is " + d1.getValue() + " and d2 is " + d2.getValue());
  }
}