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
private static IMethod getSingleSelectedMethod(IStructuredSelection selection){
		if (selection.isEmpty() || selection.size() != 1) 
			return null;
		if (selection.getFirstElement() instanceof IMethod)
			return (IMethod)selection.getFirstElement();
		return null;
	}
	
	private IMethod getSingleSelectedMethod(ITextSelection selection) throws JavaModelException{
		
		
		
		
		IJavaElement[] elements= resolveElements();
		if (elements.length > 1)
			return null;
		if (elements.length == 1 && elements[0] instanceof IMethod)
			return (IMethod)elements[0];
		IJavaElement elementAt= SelectionConverter.getInputAsCompilationUnit(fEditor).getElementAt(selection.getOffset());
		if (elementAt instanceof IMethod)
			return (IMethod)elementAt;
		return null;
	}
	
	private static boolean canRunOn(IMethod method) throws JavaModelException{
		return ChangeSignatureRefactoring.isAvailable(method);
	}
	
	private static ChangeSignatureRefactoring createRefactoring(IMethod method) throws JavaModelException{
		return ChangeSignatureRefactoring.create(method);