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Eclipse Platform
Release 3.5

org.eclipse.ltk.core.refactoring
Class NullChange

java.lang.Object
  extended by 

org.eclipse.ltk.core.refactoring.Change
      extended by 
org.eclipse.ltk.core.refactoring.NullChange
All Implemented Interfaces:
IAdaptable

public class NullChange
extends Change

A refactoring change that does nothing. The reverse change of a NullChange is a NullChange.

Note: this class is not intended to be extended by clients.

Since:
3.0
Restriction:
This class is not intended to be subclassed by clients.

Constructor Summary
NullChange ()
          Creates a new NullChange with a default name.
NullChange ( String name)
          Creates a new NullChange with the given name.
 
Method Summary
  Object getModifiedElement ()
          Returns the element modified by this Change.
  String getName ()
          Returns the human readable name of this change.
 void initializeValidationData ( IProgressMonitor pm)
          Hook method to initialize some internal state to provide an adequate answer for the isValid method.
  RefactoringStatus isValid ( IProgressMonitor pm)
          Verifies that this change object is still valid and can be executed by calling perform.
  Change perform ( IProgressMonitor pm)
          Performs this change.
 
Methods inherited from class org.eclipse.ltk.core.refactoring. Change
dispose, getAdapter, getAffectedObjects, getDescriptor, getParent, isEnabled, setEnabled, setEnabledShallow
 
Methods inherited from class java.lang. Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

NullChange

public NullChange()
Creates a new NullChange with a default name.


NullChange

public NullChange(
String name)
Creates a new NullChange with the given name.

Parameters:
name - the human readable name of this change
Method Detail

getName

public 
String getName()
Returns the human readable name of this change. The name MUST not be null.

Specified by:
getName in class Change
Returns:
the human readable name of this change

initializeValidationData

public void initializeValidationData(
IProgressMonitor pm)
Hook method to initialize some internal state to provide an adequate answer for the isValid method. This method gets called after a change or a whole change tree has been created.

Typically this method is implemented in one of the following ways:

  • the change hooks up a listener on some delta notification mechanism and marks itself as invalid if it receives a certain delta. Is this the case the implementor must take care of unhooking the listener in dispose.
  • the change remembers some information allowing to decide if a change object is still valid when isValid is called.

For example, a change object that manipulates the content of an IFile could either listen to resource changes and detect that the file got changed or it could remember some content stamp and compare it with the actual content stamp when isValid is called.

Specified by:
initializeValidationData in class Change
Parameters:
pm - a progress monitor

isValid

public 
RefactoringStatus isValid(
IProgressMonitor pm)
                          throws 
CoreException
Verifies that this change object is still valid and can be executed by calling perform. If a refactoring status with a severity of RefactoringStatus.FATAL is returned then the change has to be treated as invalid and can no longer be executed. Performing such a change produces an unspecified result and will very likely throw an exception.

This method is also called by the UndoManager to decide if an undo or redo change is still valid and therefore can be executed.

Specified by:
isValid in class Change
Parameters:
pm - a progress monitor.
Returns:
a refactoring status describing the outcome of the validation check
Throws:
CoreException - if an error occurred during validation check. The change is to be treated as invalid if an exception occurs

perform

public 
Change perform(
IProgressMonitor pm)
               throws 
CoreException
Performs this change. If this method is called on an invalid or disabled change object the result is unspecified. Changes should in general not respond to IProgressMonitor.isCanceled() since canceling a change tree in the middle of its execution leaves the workspace in a half changed state.

Specified by:
perform in class Change
Parameters:
pm - a progress monitor
Returns:
the undo change for this change object or null if no undo is provided
Throws:
CoreException - if an error occurred during change execution

getModifiedElement

public 
Object getModifiedElement()
Returns the element modified by this Change. The method may return null if the change isn't related to an element.

Specified by:
getModifiedElement in class Change
Returns:
the element modified by this change

Eclipse Platform
Release 3.5

Guidelines for using Eclipse APIs.

Copyright (c) Eclipse contributors and others 2000, 2008. All rights reserved.


 
 
  Published under the terms of the Eclipse Public License Version 1.0 ("EPL") Design by Interspire