Put the Mouse Down and Step Away from the Keyboard

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Revision as of 03:04, 7 March 2009 by BurkHufnagel (Talk | contribs)
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While cleaning up some legacy code, I found a method designed to verify that a formatted string contained a valid time. The expected format was “hh:mm:ss xx”, where ‘hh’ represents the hour, ‘mm’ represents minutes, ‘ss’ represents seconds, and ‘xx’ is either ‘AM’ or ‘PM’. It seemed fairly long so I took a closer look.

The method used the following code to convert two characters (representing the hour) into a number, and verify that it was within the proper range:

try {
    Integer.parseInt( time.substring(0, 2) );
} catch ( Exception x ) {
    return false;
}

if ( Integer.parseInt(time.substring(0, 2) ) > 12) {
    return false;
}

The same basic code appeared twice more, with appropriate changes to the character offset and upper limit, to test the minutes and seconds. The method ended with these lines to test for ‘AM’ or ‘PM’:

if ( !time.substring(9, 11).equals("AM") & !time.substring(9, 11).equals("PM") ) {
    return false;
}

If none of the previous code found a problem and returned “false” then the method returned “true”.

If the preceding code seems wordy and difficult to follow, don’t worry. Even an experienced Java developer might think the same; which meant I’d found something worth cleaning up. I refactored it and wrote a few unit tests - just to make sure it still worked.

I felt pleased with the results. The new version was easier to read, half the size, and more accurate because the original code had only tested the upper boundary for the hour, minutes, and seconds.

While getting ready for work the next day, an idea popped in my head; why not use a regular expression to validate the string? After a few minutes typing, I had a new implementation that only needed one line of code. It worked, but it felt too complicated so I split it in two to make it more readable. Here it is:

public static boolean validateTime( String time ) {
    String REGEX_PATTERN = "(0[1-9]|1[0-2]):[0-5][0-9]:[0-5][0-9] ([AP]M)";
    return time.matches( REGEX_PATTERN );
}

The point of this story is not that I eventually replaced over thirty lines of code with just two. The point is that until I got away from the computer, I thought my first attempt was the best solution to the problem.

If you’re an experienced programmer, this scenario may sound familiar. It often goes like this: You’ve been focused for hours on some gnarly problem and there's no solution in sight. You get up to stretch your legs, or to hit the vending machines, and on the way back the answer suddenly becomes obvious.

The trick is that while you’re coding, the logical part of your brain is active and the creative side is shut out. It can’t present anything to you until the logical side takes a break. So put the mouse down, and step away from the keyboard. The insights you gain may surprise you.

By BurkHufnagel


This work is licensed under a Creative Commons Attribution 3

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