Class 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 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()
        Description copied from class: Change
        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)
        Description copied from class: Change
        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
        Description copied from class: Change
        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
        Description copied from class: Change
        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()
        Description copied from class: Change
        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