Bug 67168 Change Signature shows error message twice [refactoring]
200406111814 public class TestClass { void change() { } x } Try to 'Change Method Signature' on 'change()'. The error message dialog always shows up twice.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/ModifyParametersAction.java
if (canEnable(selection)) 
				startRefactoring(getSingleSelectedMethod(selection));
		} catch (JavaModelException e) {
			ExceptionHandler.handle(e, RefactoringMessages.getString("OpenRefactoringWizardAction.refactoring"), RefactoringMessages.getString("OpenRefactoringWizardAction.exception")); 
		}
	}
    /*
     * @see SelectionDispatchAction#run(ITextSelection)
     */
	public void run(ITextSelection selection) {
		try {
			if (!ActionUtil.isProcessable(getShell(), fEditor))
				return;
			IMethod singleSelectedMethod= getSingleSelectedMethod(selection);
			if (canRunOn(singleSelectedMethod)){
				startRefactoring(singleSelectedMethod);
			} else {
				String unavailable= RefactoringMessages.getString("ModifyParametersAction.unavailable"); 
				MessageDialog.openInformation(getShell(), RefactoringMessages.getString("OpenRefactoringWizardAction.unavailable"), unavailable); 
			}
		} catch (JavaModelException e) {
			ExceptionHandler.handle(e, RefactoringMessages.getString("OpenRefactoringWizardAction.refactoring"), RefactoringMessages.getString("OpenRefactoringWizardAction.exception")); 
		}
	}
		
	private static boolean canEnable(IStructuredSelection selection) throws JavaModelException{
		return canRunOn(getSingleSelectedMethod(selection));
	}