Following code snippet should write 0.0 to the output:

        DoubleProperty p0 = new SimpleDoubleProperty(0.0);
        DoubleProperty p05 = new SimpleDoubleProperty(0.5);
        
        DoubleProperty p1 = new SimpleDoubleProperty(1.0);
        DoubleProperty p2 = new SimpleDoubleProperty(2.0);
        
        p1.bindBidirectional(p2);
        
        p1.bind(p0);
        try {
        p2.set(0.5);
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        System.out.println(p2.get());

The problem is that setting or binding a bidirectionally bound property (+ the counterpart property is unidirectionally bound) results in an Exception. The old value will not be restored however.