if (oldMethod == null) return new HashSet(0);
	private static Set getOldErrorMessages(TextEdit edit, CompilationUnit cuNode) {		MethodDeclaration oldMethod= getMethodDeclaration(edit, null, cuNode);		Message[] oldMessages= ASTNodes.getMessages(oldMethod, ASTNodes.INCLUDE_ALL_PARENTS);		Set messageSet= new HashSet(oldMessages.length);		for (int i= 0; i < oldMessages.length; i++) {			messageSet.add(oldMessages[i].getMessage());		}		return messageSet;	}	