How to write a Property Change Listener in Java?

[SKREECH]

Hi folks,
Last time your solutions were really useful for me, so thought that this is the right place to post my query. Now I am stuck with the property change listener in Java.!! I know that this occur whenever the value of a bound property changes. But since I don't know much about the beans, I am not able to use this property. So requesting you all guys, please tell me how to write a Property Change Listener in Java.?? Hope that I get the same help like last time..!!

[void]

Whenever the value of a bound property changes for a bean, property-change events occurs. You should first know properly about the beans, then only you can understand this listener. JavaBeans is a portable, platform-independent component model written in the Java programming language. You can create reuseable, platform-independent components, by using the JavaBeans API. Normally JavaBeans are called as beans. You can change or customize the beans, since they are dynamic in nature. For communication with the other beans, the beans use an events. Beans expose properties so they can be customized at design time.

[Warner]

You may need the property change listener many times. The following are some conditions where you have to use the property-change listeners :

1. You need a way to detect when the user has entered a new value after implementing a formatted text field. For listening to changes on the value property, you will have to register a property-change listener on the formatted text field.
2. You have implemented a dialog. By doing this you can know when a user has clicked one of the dialog's buttons or changed a selection in the dialog.
3. You can register a property-change listener on the keyboard focus manager to listen to changes to the focusOwner property.

[Allan.d]

I have provided you with a sample of the coding that can help you for writing a property-change listener in Java :

KeyboardFocusManager focusManager =
   KeyboardFocusManager.getCurrentKeyboardFocusManager();
focusManager.addPropertyChangeListener(new FocusManagerListener());
...
public FocusManagerListener() implements PropertyChangeListener {
    public void propertyChange(PropertyChangeEvent e) {
        String propertyName = e.getPropertyName();
        if ("focusOwner".equals(propertyName) {
            ...
        } else if ("focusedWindow".equals(propertyName) {
            ...
        }
    }
    ...
}

[opaper]

Registration of a property is very important, otherwise you cannot use that. I have given the coding that shows how to register a property change listener on the value property :

double amount;
JFormattedTextField amtField;
...
amtField.addPropertyChangeListener("value",
                                      new FormattedTextFieldListener());
...
class FormattedTextFieldListener implements PropertyChangeListener {
    public void propertyChanged(PropertyChangeEvent pe) {
        Object source = pe.getSource();
        if (source == amtField) {
            amt = ((Number)amountField.getValue()).doubleValue();
            ...
        }
    }
}