Checkstyle - avoiding using 'magic numbers'

[K DeLucia]

I'm pretty new to java and have just discovered CheckStyle. One of the messages I'm getting a lot of is # 'is a magic number'.

In one case I worked around it like this:

 
final int zipLength = 11;
if (zip == null) {
	msgs.add("Zip code is required.\n");
	validationFailed = true;
} else if (zip.length() >= zipLength) {
	msgs.add("Zip code cannot exceed 10 characters.\n");
	validationFailed = true;
}
   

But what should I do in a case where I have a lot of numbers like this:

if (recordType.equals("Customer")) {
	stmt.setString(1, wildcard);
	stmt.setInt(2, store);
	stmt.setString(3, idType);
	stmt.setInt(4, idNum);
	stmt.setString(5, unempID);
	stmt.setString(6, fname);
	stmt.setString(7, lname);
	stmt.setString(8, phone);
	stmt.setString(9, street);
	stmt.setString(10, street2);
	stmt.setString(11, city);
	stmt.setString(12, state);
	stmt.setString(13, zip);
	stmt.setString(14, email);
	stmt.setTimestamp(15, new java.sql.Timestamp(System
						.currentTimeMillis()));
	stmt.setString(16, verify);
	stmt.setString(17, hh);
   

Is there some other way I should be doing this? Thanks for any input!

[Ernest Friedman-Hill]

Well, in this particular case, it's much nicer to use column names rather than column numbers; this makes your code far more robust to database schema changes.

[Rob Spoor]

K DeLucia wrote:But what should I do in a case where I have a lot of numbers like this:

If you still want to use the numbers, you can always use a counter:

int index = 1;
stmt.setString(index++, wildcard);
stmt.setInt(index++, store);
stmt.setString(index++, idType);
stmt.setInt(index++, idNum);
stmt.setString(index++, unempID);
stmt.setString(index++, fname);
...

Added bonus is that you can add a field in between without having to re-index. A downside is that the order is still important.

[Sridhar Santhanakrishnan]

What about cases where the numbers are not related?
I recently had to use iText to generate some Pdfs. There were so many numbers that I finally had to convince people to ignore those warnings.

[Jeanne Boyarsky]

I have my static analysis utility configured to ignore magic numbers above a certain threshold. (I think it is 10 or 15) to avoid the JDBC code being triggered. I don't like using the column names because if they change in the SQL, I have to remember to change them in the get/set methods. For the rare occasions where my JDBC code uses a ton of columns, I configure the static analysis tool to suppress the errors.

In your first example with the zip code, the tool is right. You do have a "magic number" in the code. You didn't work around it - you fixed a problem. It's traditional to use a real constant for this like:
private static final int ZIP_LENGTH = 11;

[Jeanne Boyarsky]

Sridhar Santhanakrishnan wrote:What about cases where the numbers are not related?
I recently had to use iText to generate some Pdfs. There were so many numbers that I finally had to convince people to ignore those warnings.

Why do yo have so many numbers in iText? I have mainly column widths in my iText code - which are all constants anyway. What other types of numbers do you have?