Do you indent your code for good or evil? Of all the horrors that afflict the pilgrim programmer, evil indentation is the most horrific. The horrifying lack thereof, the horrifying use of tabs, the horrifying concoction of tabs and spaces, the ... well, read on fellow coder, and face the horror yourself!

But first, ask yourself one question: why do we indent? why do we bother? What is it in our very nature that makes indentation the first principal of coding?

Source code is all about structured logic. When you make it easy to see the logic, then the program is easy to read. That's why we indent. The first, foremost and only reason: it makes code easier to read. All else follows.

That's why I really have to wonder when I see badly-indented code. Do these coders care nothing for the ethics of the profession? How can they so callously cast these cancerous texts upon us? Do they care nothing for themselves? Will they not have to maintain these corrugations, six months hence? Do they secretly enjoy all-nighters and death marches? Perhaps...

So, in the interests of the programmer-on-the-street, I hereby lay down the evils of indentation. A how NOT to do it guide, if you will. If you have never consciously considered these great questions before now, if you have simply followed the pathetic example of your peers, the perilous proclivities of your peripatetic tutors, or the prescriptions of your workplace, then think now, or forever hold yourself back. Indentation is a detail that has to sweat.

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Here then are the evils of indentation. There's a suitably evil number of them: four.

The First Evil: To Tabulate

for( fs = 0; fs < sake; fs++ ) {
        thisIsNuts();
        if( mindcapacity < nineitems ) {
                fire();
        }
}

Hey, you know what? Tabs were invented for typewriters. In the modern software development environment, the tab key stands for only one thing: move this line of code to the correct indentation. It does not mean: insert a tab character. Just because you have tabs set up to show as four spaces as a kludge, does not mean that that the rest of the programming world thinks this is a good idea.

Tab characters will show up differently all over the place. The whole point of indentation is lost if the indentation is not the same for all developers on the project. Think of the children! For goodness sake stick to spaces. Every time you hit tab your IDE should insert the correct number of spaces to bring your code to the current indentation column. And that's it. Nothing fancy. But now, guess what? It looks the same for everyone. Do you realise how many lives you just saved? How many premature heart attacks you prevented?

The Second Evil: To Make Too Much Space

public void removeContext() {
    if( spacedOut() ) {
        line >>> allthewayover;
        meaning = inview ? ok : emptyspace;
    }
}

So you like to indent by four spaces. Sure. Are you nuts? what a waste of screen real-estate. One of the biggest aids to program comprehension is ... code on the screen. Yup, the more code you can see the better. Get a bigger monitor and see the difference. So with your IDE of choice squashing the code window from all sides, you really need to avoid pushing code off to the right. It just disappears out of sight and out of mind.

So keep it to two spaces. Always and forever. There is no other way to optimise this. One space is not clear enough. Three spaces is bizarre. Four is wasteful. Anything more, like say, eight (Some people actually do this - God help us all), and you should be fired for wasting bytes.

OK, I'll relax a bit. Sometimes you can use four spaces to indent. When there is a substantial change of context, for example, anonymous inner classes (they are freaky enough to warrant their own rule, don't you think?), then it makes sense. It's a good visual clue that something a bit different is going on.

The Third Evil: To Stray From The Path

if( logic ) {
    canbefollowed();
  } else if( logic ) {
isclear();
} else {
    runaway();
}
  crying();

So you've changed the settings on your IDE, you use two spaces, tab inserts two spaces, and auto-indents to the correct level, and you're sitting pretty. Not so fast, flyboy.

You are indenting everywhere right? And I mean, everywhere. There is no point doing it in a few places and getting lazy when you do your usual cut-and-paste coding anti-pattern. Or you make some changes to code that was written by someone else and you just, ignore the indentation. Sure it's only here and there. Bzzzt! can you say spaghetti code?

Stick to the one true path: indent everything, and never mix tabs and spaces.

A foolish consistency may be the hobgoblin of little minds, but you're not writing poetry, you're writing code. Get a small mind. A really really teeny-weeny tiny one. Get obnoxious about consistency and the coding brethren (that's a gender-neutral term, by the way) will thank you! Come on, neat code just makes your day.

The Fourth Evil: To Break The Bond

public void myProfessor()
  {
    toldMe();
    if( makeCodeReallyReallyClear() ) 
      {
        thenIAmGood();
      }
    else
      {
        actuallyIAmWasteOfSpace();
      }
  } 

So this one is a bit of thrown gauntlet. Here's the question: what does each level of indentation signify? Well? It's not hard...

One level of logic. Just one. Not two. One. Each level of indentation says we've gone a one level deeper into the decision structure. There is an intrinsic bond between indent and logic. Keep to this rule and your eye can scan the code and see that it is good. You can pick out the flow of the code from 300 yards and hit the target with your back turned using a mirror.

So why, oh why, do some people find it necessary to indent two levels, wasting a line into the bargain? Not a chance you can justify this. Maybe someone took a beginners design course where they were told that whitespace was good. Sure it is. But, you know, all things in moderation...

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Come on people! There are no excuses. Most source editors will auto-indent for you anyway. Let's get with the program and remove this root of programmer pain. We have enough to worry about with demanding managers, impossible deadlines and long hours. Let's just do each other a favour.

In case you think I'm all talk and no action, here's the action. You can scour my code for indentation evils. I have an open source project, Jostraca, that's been around for about five years and has had plenty of time to build up a bit of cruft in the codebase. So get going! Everybody who finds a violation will get a FREE CSV Manager single developer license, worth $97. Oh yes, that's real money.

Here are the rules: you have to be the first to find and post the example of incorrect indentation in the comments to this entry. You have to state which evil is being perpetrated. If you're second fiddle, tough luck. The example has to be taken from the latest release (1.4.0). Generated code and non-Java code don't count so don't bother looking there. Oh, and I reserve the right to invent new rules if I feel like it.

So come on, are you gonna bankrupt me for mouthing off or what?