In my limited experience, I've been on several projects that have had some sort of string utility class with methods to determine if a given string is a number. The idea has always been the same, however, the implementation has been different. Some surround a parse attempt with try/catch
public boolean isInteger(String str) {
try {
Integer.parseInt(str);
return true;
} catch (NumberFormatException nfe) {}
return false;
}
and others match with regex
public boolean isInteger(String str) {
return str.matches("^-?[0-9]+(\.[0-9]+)?$");
}
Is one of these methods better than the other? I personally prefer using the regex approach, as it's concise, but will it perform on par if called while iterating over, say, a list of a several hundred thousand strings?
Note: As I'm kinda new to the site I don't fully understand this Community Wiki business, so if this belongs there let me know, and I'll gladly move it.
EDIT:
With all the TryParse suggestions I ported Asaph's benchmark code (thanks for a great post!) to C# and added a TryParse method. And as it seems, the TryParse wins hands down. However, the try catch approach took a crazy amount of time. To the point of me thinking I did something wrong! I also updated regex to handle negatives and decimal points.
Results for updated, C# benchmark code:
00:00:51.7390000 for isIntegerParseInt
00:00:03.9110000 for isIntegerRegex
00:00:00.3500000 for isIntegerTryParse
Using:
static bool isIntegerParseInt(string str) {
try {
int.Parse(str);
return true;
} catch (FormatException e){}
return false;
}
static bool isIntegerRegex(string str) {
return Regex.Match(str, "^-?[0-9]+(\.[0-9]+)?$").Success;
}
static bool isIntegerTryParse(string str) {
int bob;
return Int32.TryParse(str, out bob);
}
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