String to Int in java - Likely bad data, need to avoid exceptions

Question

Seeing as Java doesn\'t have nullable types, nor does it have a TryParse(), how do you handle input validation without throwing an exceptions?

The usual way:

Answer 1

The above code is bad because it is equivalent as the following.

// this is bad
int val = Integer.MIN_VALUE;
try
{
   val = Integer.parseInt(userdata);
}
catch (NumberFormatException ignoreException) { }

The exception is ignored completely. Also, the magic token is bad because an user can pass in -2147483648 (Integer.MIN_VALUE).

The generic parse-able question is not beneficial. Rather, it should be relevant to the context. Your application has a specific requirement. You can define your method as

private boolean isUserValueAcceptable(String userData)
{
   return (    isNumber(userData)    
          &&   isInteger(userData)   
          &&   isBetween(userData, Integer.MIN_VALUE, Integer.MAX_VALUE ) 
          );
}

Where you can documentation the requirement and you can create well defined and testable rules.