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package javafx.beans.value;

A ChangeListener is notified whenever the value of an ObservableValue changes. It can be registered and unregistered with ObservableValue.addListener(ChangeListener) respectively ObservableValue.removeListener(ChangeListener) 
 For an in-depth explanation of change events and how they differ from invalidation events, see the documentation of ObservableValue. 
 The same instance of ChangeListener can be registered to listen to multiple ObservableValues. 
See Also:
ObservableValue
Since:
JavaFX 2.0/**
 * A {@code ChangeListener} is notified whenever the value of an
 * {@link ObservableValue} changes. It can be registered and unregistered with
 * {@link ObservableValue#addListener(ChangeListener)} respectively
 * {@link ObservableValue#removeListener(ChangeListener)}
 * <p>
 * For an in-depth explanation of change events and how they differ from
 * invalidation events, see the documentation of {@code ObservableValue}.
 * <p>
 * The same instance of {@code ChangeListener} can be registered to listen to
 * multiple {@code ObservableValues}.
 *
 * @see ObservableValue
 *
 *
 * @since JavaFX 2.0
 */
@FunctionalInterface
public interface ChangeListener<T> {

    
This method needs to be provided by an implementation of ChangeListener. It is called if the value of an ObservableValue changes. 

In general, it is considered bad practice to modify the observed value in
this method.
Params:
observable –  The ObservableValue which value changed
oldValue – 
           The old value
newValue – 
           The new value/**
     * This method needs to be provided by an implementation of
     * {@code ChangeListener}. It is called if the value of an
     * {@link ObservableValue} changes.
     * <p>
     * In general, it is considered bad practice to modify the observed value in
     * this method.
     *
     * @param observable
     *            The {@code ObservableValue} which value changed
     * @param oldValue
     *            The old value
     * @param newValue
     *            The new value
     */
    void changed(ObservableValue<? extends T> observable, T oldValue, T newValue);
}