/**
* Undo effect of command.
*
* @exception CannotUndoException if the command cannot be undone or has not been executed before.
*/
public void undo() throws CannotUndoException {
// the CommandProcessor should prevent us from being called
// without a successful prior execute, just be safe here
MSystem system = fSystemState.system();
if (system.activeOperation() != fOpCall) throw new CannotUndoException("no undo information");
system.popOperation();
system.setCurrentState(fSystemState);
}
/**
* Executes command and stores undo information.
*
* @exception CommandFailedException if the command failed.
*/
public void execute() throws CommandFailedException {
fSystemState.system().enterOperation(fOpCall, new PrintWriter(Log.out()));
}