Details in Java Code: Error Reporting and Loop Control Variables

Sometimes, it’s easy to focus so much on the architecture of a system that the details of its implementation get lost. While it’s true that inattention to architectural concerns can cause a system to fail, it’s also true that poor attention to the details can undermine even the best overall system design. This post covers a few minor details of code structure that I’ve found to be useful in my work:

It’s a small thing, but one of my favorite utility methods is a short way to throw run-time exceptions.

    public static void FAIL(String message)
        throw new RuntimeException(message);

Defining this method accomplishes a few useful goals. The first is that (with an import static) it makes it possible to throw a RuntimeException with 22 fewer characters of source text per call site. If you’re writing usefully descriptive error messages (which you should be), this can significantly improve the readability of the code. The text FAIL tends to stand out in source code listings, and bringing the error message closer to the left margin of the source text makes it more obvious. The symbol FAIL is also easy to identify with tools like grep, ack, and M-x occur.

To handle re-throw scenarios, it's also useful to have another definition that lets you specify a cause for the failure.

    public static void FAIL(String message, Throwable cause)
        throw new RuntimeException(message, cause);

Related to this is a useful naming convention for loop control variables. Thanks in large part to FORTRAN, and its mathematical heritage, it's very common to use the names i, j, and k for loop control variables. These names aren't very descriptive, but they're short and for small loop bodies, there's usually enough context that a longer name would be superfluous. (If your loop spans pages of text, you should use a more descriptive variable name... but first, you should try to break up your loop into sensible, testable functions.) One technique I've found useful for making loop control variables more obvious (and searchable) without going to fully descriptive variable names is to double up the letters, giving ii, jj, and kk.

These are both small changes, but they both can improve the readability of the code. Try them out and see if you like them. If you disagree that they are improvements, it's easy to switch back.

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