Noob question, how to avoid this runtime error,please help..

Question

Im new to java. Im using a JOptionPane in getting the user an input/a number, which is in String,. and to use it, im converting it by Integer.parseInt. When I run it everything seems ok, but whenever i inputted other data types other than integer(e.g char), i get a runtime error message "exception in main thread java.lang.NumberFormatException blah blah.....,. Is theres a way or a method or something that i can filter the users input when they type a character or when they inputted nothing that will not resulted to a runtime error, instead, an error message box will said that it is an invalid input. thanks in advance

Answer 1

Ah, well, after an evening of rest and reflection, I have to conclude that we are all partially correct. I never meant to imply that NumberFormatException should not be caught. I have had to repair too many classes in which just-in-case or programming-by-exception was a rule, rather than a valuable technique for handling exceptional or error situations.
As far as this example, I was not attempting to write a parser, or even start one. We are talking about a very simple situation ... determine if a String represents an integer. My example was overly simple, too. As pointed out, too simple. *\d+* would have eliminated empty strings, and with a few relatively minor changes, could handle all legal integers easily, including '-' and ',' characters, while excluding floating point and other invalid inputs. I did mention that regexes were an advanced technique. A Scanner could be used to test for the existence of an integer in a string. None of these rise to the level of parsing, IMO, but, as I have frequently said in these fora, the arguments of the mages are infinite. Of course, that implies that I consider myself a mage, which is not actually the truth.
In any case, as pointed out, this is an example where catching a runtime exception is probably a good idea, as long as we don't give the OP the idea that this is the only technique, or that code can be written to ignore the causes of exceptional situations, because we can always handle them in the catch block. I have seen way too much of this to be comfortable with even the suggestion of this.
I come here to learn. Sometimes, I learn interesting, complex things. Sometimes, I learn interesting, simple things.
Sincerely, thanks for helping me to learn.
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