public class MyContainer {

    // implements property change support
    private PropertyChangeSupport changeSupport = ...;

    // this is the observable object
    private MyData data;

    public void addPropertyChangeListener(PropertyChangeListener l) {...}
    public void removePropertyChangeListener(PropertyChangeListener l) {...}
    public void firePropertyChange(String propertyName, Object oldValue, Object newValue) {...}

    public MyData getData() {...}

    public MyData setData(MyData newValue) {
            // create oldValue from member
            MyData oldValue = data.clone();
 
            // Mutate member instead of replacing the reference
            data.setAttributes(newValue);

            // fire change and provide correct old and new value
            firePropertyChange("data", oldValue, data);
    }
}

private void notifyIfChanged(ValueDiff<? extends T> diff) {
        if (hasListeners()) {
            // here diff.getOldValue() is not considered
            T oldValue = cachedValue;

            // here diff.getNewValue() is not considered
            T newValue = cachedValue = property.getValue(source);
    
            if (diff == null)
                    diff = Diffs.createValueDiff(oldValue, newValue);
            if (!Util.equals(oldValue, newValue) || stale) {
                    stale = false;
                    // here diff is transmitted untouched in case it is not null
                    fireValueChange(Diffs.unmodifiableDiff(diff));
            }
        }
}