Use exception to control flow?

Question

I use validateExcelFile(File excelFile) to validate whether a file has valid excel format,
when file is in invalid format, I have two options:
1) return the error message in validate method:
public String validateExcelFile(File excelFile) {
String errorMsg = "";
if(errorMsg.length == 0) {
return null;
} else {
return errorMsg;
Or
2)Throw out a exception containing errorMsg
public void validateExcelFile(File excelFile)
throws InvalidExcelFormatException {
String errorMsg = "";
if(errorMsg.length != 0) {
throw new InvalidExcelFormatException(errorMsg);
The context in which the validate method is invoked needs to delete any invalid excel file according to the validate result, option 2 has the good that if there is another validate method and it also throws out the same exception when a file is invalid then I can place the two method in one
try{
validateMethod1( excelFile );
validateMethod2( excelFile );
} catch (InvalidFormatException ex) {  // deletes invalid file } statement, it is more clear than to check every method's returned error message, but I doubt whether it is good practice to control flow with exception instead of
flow statements like if.
Thanks.
StuartS
Edited by: StuartS on Oct 24, 2007 8:35 PM

Answer 1

TimSparq wrote:
You are correct, it is best practice not to controll flow with exceptions.
Perhaps your validate message could just return a boolean and you can do something like:
if (!validateExcelFile(file)) {
// delete file
Yeah, I was thinking of it more from a security validation standpoint, but if you simply want to accomplish an action as the result of a bad format, then you're definitely better off having a boolean function.