org.jscience.util
Interface ChangeListener

All Superinterfaces:
java.util.EventListener
All Known Implementing Classes:
ChangeAdapter, ChangeForwarder, ChangeForwarder.Retyper, ChangeListener.AlwaysVetoListener, ChangeListener.LoggingListener

public interface ChangeListener
extends java.util.EventListener

Interface for objects which listen to ChangeEvents.

Since:
1.1

Nested Class Summary
static class ChangeListener.AlwaysVetoListener
          An implementation that always vetoes everything.
static class ChangeListener.LoggingListener
          A listener that writes information about the event stream to a PrintStream.
 
Field Summary
static ChangeListener ALWAYS_VETO
          Convenience implementation which vetoes every change of which it is notified.
static ChangeListener LOG_TO_OUT
          Convenience implementation that echoes all events to out.
 
Method Summary
 void postChange(ChangeEvent cev)
          

Called when a change has just taken place.

 void preChange(ChangeEvent cev)
          

Called before a change takes place.

 

Field Detail

ALWAYS_VETO

static final ChangeListener ALWAYS_VETO
Convenience implementation which vetoes every change of which it is notified. You could add this to an object directly to stop it changing in any way, or alternatively you could add it for a specific ChangeType to stop that single item from altering.


LOG_TO_OUT

static final ChangeListener LOG_TO_OUT
Convenience implementation that echoes all events to out.

Method Detail

preChange

void preChange(ChangeEvent cev)
               throws ChangeVetoException

Called before a change takes place.

This is your chance to stop the change by throwing a ChangeVetoException. This method does not indicate that the change will definitely take place, so it is not recomended that you take any positive action within this handler.

Parameters:
cev - An event encapsulating the change which is about to take place.
Throws:
ChangeVetoException - Description of Exception
ChangeVetoException - if the receiver does not wish this change to occur at this time.

postChange

void postChange(ChangeEvent cev)

Called when a change has just taken place.

This method is the place to perform any behavior in response to the change event.

Parameters:
cev - An event encapsulating the change which has occured.