How to Write Unmaintainable Code (1999)
How To Write Unmaintainable Code




Last updated Thursday, 18-Nov-1999 20:27:28 PDT by Roedy
Green ©1997-1999 Canadian Mind Products.
This essay is also available in Spanish.
In the interests of creating employment opportunities in the Java programming
field, I am passing on these tips from the masters on how to write code
that is so difficult to maintain, that the people who come after you will
take years to make even the simplest changes. Further, if you follow all
these rules religiously, you will even guarantee yourself a lifetime
of employment, since no one but you has a hope in hell of maintaining the
code.

General Principles
To foil the maintenance programmer, you have to understand how he thinks.
He has your giant program. He has no time to read it all, much less understand
it. He wants to rapidly find the place to make his change, make it and
get out and have no unexpected side effects from the change.
He views your code through a tube taken from the centre of a roll of
toilet paper. He can only see a tiny piece of your program at a time. You
want to make sure he can never get the big picture from doing that. You
want to make it as hard as possible for him to find the code he is looking
for. But even more important, you want to make it as awkward as possible
for him to safely ignore anything.

Specific Techniques



Lie in the comments. You don't have to actively lie, just fail to keep
comments as up to date with the code.


Pepper the code with comments like /* add 1 to i */ however, never
document wooly stuff like the overall purpose of the package or method.


Make sure that every method does a little bit more (or less) than its name
suggests. As a simple example, a method named
isValid(x) should
as a side effect convert x to binary and store the result in a database.


Use acronyms to keep the code terse. Real men never define acronyms; they
understand them genetically.


In the interests of efficiency, avoid encapsulation. Callers of a method
need all the external clues they can get to remind them how the method
works inside.


If, for example, you were writing an airline reservation system, make sure
there are at least 25 places in the code that need to be modified if you
were to add another airline. Never document where they are. People who
come after you have no business modifying your code without thoroughly
understanding every line of it.


In the name of efficiency, use cut/paste/clone/modify. This works much
faster than using many small reusable modules.


Never never put a comment on a variable. Facts about how the variable
is used, its bounds, its legal values, its implied/displayed number of
decimal points, its units of measure, its display format, its data entry
rules (e.g. total fill, must enter), when its value can be trusted etc.
should be gleaned from the procedural code. If your boss forces you to
write comments, lard method bodies with them, but never comment a variable,
not even a temporary!


Try to pack as much as possible into a single line. This saves the overhead
of temporary variables, and makes source files shorter by eliminating new
line characters and white space. Tip: remove all white space around operators.
Good programmers can often hit the 255 character line length limit imposed
by some editors. The bonus of long lines is that programmers who cannot
read 6 point type must scroll to view them.


Cd wrttn wtht vwls s mch trsr. When using abbreviations inside variable
or method names, break the boredom with several variants for the same word,
and even spell it out longhand once in while. This helps defeat those lazy
bums who use text search to understand only some aspect of your program.
Consider variant spellings as a variant on the ploy, e.g. mixing International
colour,
with American color and dude-speak
kulerz. If you spell out
names in full, there is only one possible way to spell each name. These
are too easy for the maintenance programmer to remember. Because there
are so many different ways to abbreviate a word, with abbreviations, you
can have several different variables that all have the same apparent purpose.
As an added bonus, the maintenance programmer might not even notice they
are separate variables.


Never use an automated source code tidier to keep your code aligned. Lobby
to have them banned them from your company on the grounds they create false
deltas in PVCS (version control tracking) or that every programmer should
have his own indenting style held forever sacrosanct for any module he
wrote. Banning them is quite easy, even though they save the millions of
keystrokes doing manual alignment and days wasted misinterpreting poorly
aligned code. Just insist that everyone use the
same tidied format,
not just for storing in the common repository, but while they are editing.
This starts an RWAR and the boss, to keep the peace, will ban automated
tidying. Without automated tidying, you are now free to accidentally
misalign the code to give the optical illusion that bodies of loops and
ifs are longer or shorter than they really are, or that else clauses match
a different if than they really do. e.g.

if (a)
  if (b) x = y;
else x = z;


Never put in any { } surrounding your if/else blocks unless they are syntactically
obligatory. If you have a deeply nested mixture of if/else statements and
blocks, especially with misleading indentation, you can trip up even an
expert maintenance programmer.


Rigidly follow the guidelines about no goto, no early returns, and no labelled
breaks especially when you can increase the if/else nesting depth by at
least 5 levels.


Use very long variable names that differ from each other by only one character,
or only in upper/lower case. An ideal variable name pair is swimmer
and swimner. Exploit the failure of most fonts to clearly discriminate
between
ilI1| or oO08 with identifier pairs like
parselnt
and parseInt or D0Calc and
DOCalc. l
is an exceptionally fine choice for a variable name since it will, to the
casual glance, masquerade as the constant 1. Create varible names that
differ from each other only in case e.g. HashTable and Hashtable.


Wherever scope rules permit, reuse existing unrelated variable names. Similarly,
use the same temporary variable for two unrelated purposes (purporting
to save stack slots). For a fiendish variant, morph the variable, for example,
assign a value to a variable at the top of a very long method, and then
somewhere in the middle, change the meaning of the variable in a subtle
way, such as converting it from a 0-based coordinate to a 1-based coordinate.
Be certain not to document this change in meaning.


Use lower case l to indicate long constants. e.g. 10l is more likely to
be mistaken for 101 that 10L is.


Ignore the conventions in Java for where to use upper case in variable
and class names i.e. Classes start with upper case, variables with lower
case, constants are all upper case, with internal words capitalised. After
all, Sun does (e.g. instanceof vs isInstanceOf, Hashtable). Not to worry,
the compiler won't even issue a warning to give you away. If your boss
forces you to use the conventions, when there is any doubt about whether
an internal word should be capitalised, avoid capitalising or make a random
choice, e.g. use both inputFileName and outputfilename. You can of course
drive your team members insane by inventing your own insanely complex
naming conventions then berate others for not following them. The ultimate
technique is to create as many variable names as possible that differ subtlely
from each other only in case.


Never use i for the innermost loop variable. Use anything but.
Use i liberally for any other purpose especially for non-int variables.
Similary use n as a loop index.


Never use local variables. Whenever you feel the temptation to use one,
make it into an instance or static variable instead to unselfishly share
it with all the other methods of the class. This will save you work later
when other methods need similar declarations. C++ programmers can go a
step further by making all variables global.


Never document gotchas in the code. If you suspect there may be a bug in
a class, keep it to yourself. If you have ideas about how the code should
be reorganised or rewritten, for heaven's sake, do not write them down.
Remember the words of Thumper
"If you can't say anything nice, don't
say anything at all". What if the programmer who wrote that code saw
your comments? What if the owner of the company saw them? What if a customer
did? You could get yourself fired.


To break the boredom, use a thesaurus to look up as much alternate vocabulary
as possible to refer to the same action, e.g. display, show,
present. Vaguely hint there is some subtle difference, where none
exists. However, if there are two similar functions that have a crucial
difference, always use the same word in describing both functions (e.g.
print
to mean write to a file, and to a print on a laser, and to display on the
screen). Under no circumstances, succumb to demands to write a glossary
with the special purpose project vocabulary unambiguously defined. Doing
so would be unprofessional breach of the structured design principle of
information
hiding.


In naming functions, make heavy use of abstract words like
it, everything,
data, handle,
stuff, do, routine, perform
and the digits e.g. routineX48, PerformDataFunction,
DoIt,
HandleStuff and
do_args_method.


In Java, all primitives passed as parameters are effectively read-only
because they are passed by value. The callee can modify the parameters,
but that has no effect on the caller's variables. In contrast all objects
passed are read-write. The reference is passed by value, which means the
object itself is effectively passed by reference. The callee can do whatever
it wants to the fields in your object. Never document whether a method
actually modifies the fields in each of the passed parameters. Name your
methods to suggest they only look at the fields when they actually change
them.


Never document the units of measure of any variable, input, output or parameter.
e.g. feet, metres, cartons. This is not so important in bean counting,
but it is very important in engineering work. As a corollary, never document
the units of measure of any conversion constants, or how the values were
derived. It is mild cheating, but very effective, to salt the code with
some incorrect units of measure in the comments. If you are feeling particularly
malicious, make up your own unit of measure; name it after yourself
or some obscure person and never define it. If somebody challenges you,
tell them you did so that you could use integer rather than floating point
arithmetic.


In engineering work there are two ways to code. One is to convert all inputs
to S.I. (metric) units of measure, then do your calculations then convert
back to various civil units of measure for output. The other is to maintain
the various mixed measure systems throughout. Always choose the second.
It's the American way!


I am going to let you in on a little-known coding secret. Exceptions are
a pain in the behind. Properly-written code never fails, so exceptions
are actually unnecessary. Don't waste time on them. Subclassing exceptions
is for incompetents who know their code will fail. You can greatly simplify
your program by having only a single try/catch in the entire application
(in main) that calls System.exit(). Just stick a perfectly standard set
of throws on every method header whether they could throw any exceptions
or not.


C compilers transform myArray[i] into *(myArray + i),
which is equivalent to *(i + myArray) which is equivalent to i[myArray].
Experts know to put this to good use. Unfortunately, this technique can
only be used in native classes.


If you have an array with 100 elements in it, hard code the literal 100
in as many places in the program as possible. Never use a static final
named constant for the 100, or refer to it as
myArray.length.
To make changing this constant even more difficult, use the literal 50
instead of 100/2, or 99 instead of 100-1. You can futher disguise the 100
by checking for a == 101 instead of a > 100 or a
> 99 instead of a >= 100.

Consider things like page sizes, where the lines consisting of x
header, y body, and z footer lines, you can apply the obfuscations independently
to each of these and to their partial or total sums.
These time-honoured techniques are especially effective in a program
with two unrelated arrays that just accidentally happen to both have 100
elements. There are even more fiendish variants. To lull the maintenance
programmer into a false sense of security, dutifully create the named constant,
but very occasionally "accidentally" use the literal 100 value instead
of the named constant. Most fiendish of all, in place of the literal 100
or the correct named constant, sporadically use some other unrelated named
constant that just accidentally happens to have the value 100, for now.
It almost goes without saying that you should avoid any consistent naming
scheme that would associate an array name with its size constant.

Eschew any form of table-driven logic. It starts out innocently enough,
but soon leads to end users proofreading and then shudder, even
modifying the tables for themselves.


Nest as deeply as you can. Good coders can get up to 10 levels of ( ) on
a single line and 20 { } in a single method. C++ coders have the additional
powerful option of preprocessor nesting totally independent of the nest
structure of the underlying code. You earn extra Brownie points whenever
the beginning and end of a block appear on separate pages in a printed
listing. Wherever possible, convert nested ifs into nested [? :] ternaries.


Join a computer book of the month club. Select authors who appear to be
too busy writing books to have had any time to actually write any code
themselves. Browse the local bookstore for titles with lots of cloud diagrams
in them and no coding examples. Skim these books to learn obscure pedantic
words you can use to intimidate the whippersnappers that come after you.
Your code should impress. If people can't understand your vocabulary, they
must assume that you are very intelligent and that your algorithms are
very deep. Avoid any sort of homely analogies in your algorithm explanations.


Make "improvements" to your code often, and force users to upgrade often
- after all, no one wants to be running an outdated version. Just because
they think they're happy with the program as it is, just think how much
happier they will be after you've "fixed" it! Don't tell anyone what the
differences between versions are unless you are forced to - after all,
why tell someone about bugs in the old version they might never have noticed
otherwise?


The About Box should contain only the name of the program, the names of
the coders and a copyright notice written in legalese. Ideally it should
link to several megs of code that produce an entertaining animated display.
However, it should
never contain a description of what the program
is for, its minor version number, or the date of the most recent code revision,
or the website where to get the updates, or the author's email address.
This way all the users will soon all be running on different versions,
and will attempt to install version N+2 before installing version N+1.


The more changes you can make between versions the better, you don't want
users to become bored with the same old API or user interface year after
year. Finally, if you can make this change without the users noticing,
this is better still - it will keep them on their toes, and keep them from
becoming complacent.


If you have to write classes for some other programmer to use, put environment-checking
code (getenv() in C++ / System.getProperty() in Java) in your classes'
nameless static initializers, and pass all your arguments to the classes
this way, rather than in the constructor methods. The advantage is that
the initializer methods get called as soon as the class program binaries
get loaded, even before any of the classes get instantiated, so
they will usually get executed before the program main(). In other words,
there will be no way for the rest of the program to modify these parameters
before they get read into your classes - the users better have set up all
their environment variables just the way you had them!


Choose your variable names to have absolutely no relation to the labels
used when such variables are displayed on the screen. E.g. on the screen
label the field "Postal Code" but in the code call the associated
variable
"zip".


Java lets you create methods that have the same name as the class, but
that are not constructors. Exploit this to sow confusion.


Never use layouts. That way when the maintenance programmer adds one more
field he will have to manually adjust the absolute co-ordinates of every
other thing displayed on the screen. If your boss forces you to use a layout,
use a single giant GridBagLayout, and hard code in absolute grid co-ordinates.


In Java, disdain the interface. If your supervisors complain, tell them
that Java interfaces force you to "cut-and-paste" code between different
classes that implement the same interface the same way, and they know
how hard that would be to maintain. Instead, do as the Java AWT designers
did - put lots of functionality in your classes that can only be used by
classes that inherit from them, and use lots of "instanceof" checks in
your methods. This way, if someone wants to reuse your code, they have
to extend your classes. If they want to reuse your code from two different
classes - tough luck, they can't extend both of them at once!


Make all of your leaf classes final. After all, you're done with
the project - certainly no one else could possibly improve on your work
by extending your classes. And it might even be a security flaw - after
all, isn't java.lang.String final for just this reason? If other coders
in your project complain, tell them about the execution speed improvement
you're getting.


Make as many of your variables as possible static. If
you don't
need more than one instance of the class in this program, no one else ever
will either. Again, if other coders in the project complain, tell them
about the execution speed improvement you're getting.


Keep all of your unused and outdated methods and variables around in your
code. After all - if you needed to use it once in 1976, who knows if you
will want to use it again sometime? Sure the program's changed since then,
but it might just as easily change back, you "don't want to have to reinvent
the wheel" (supervisors love talk like that). If you have left the comments
on those methods and variables untouched, and sufficiently cryptic, anyone
maintaining the code will be too scared to touch them.


On a method called makeSnafucated insert only the comment /*
make snafucated */. Never define what
snafucated means anywhere.
Only a fool does not already know, with complete certainty, what snafucated
means.


Reverse the parameters on a method called drawRectangle(height, width)
to drawRectangle(width, height) without making any change whatsoever to
the name of the method. Then a few releases later, reverse it back again.
The maintenance programmers can't tell by quickly looking at any call if
it has been adjusted yet. Generalisations are left as an exercise for the
reader.


Instead of using a parameters to a single method, create as many separate
methods as you can. For example instead of
setAlignment(int alignment)
where alignment is an enumerated constant, for left, right, center, create
three methods: setLeftAlignment, setRightAlignment, and
setCenterAlignment. Of course, for the full effect, you must clone
the common logic to make it hard to keep in sync.


The Kama Sutra technique has the added advantage of driving any
users or documenters of the package to distraction as well as the maintenance
programmers. Create a dozen overloaded variants of the same method that
differ in only the most minute detail. I think it was Oscar Wilde who observed
that positions 47 and 115 of the Kama Sutra were the same except in 115
the woman had her fingers crossed. Users of the package then have to carefully
peruse the long list of methods to figure out just which variant to use.
The technique also balloons the documentation and thus ensures it will
more likely be out of date. If the boss asks why you are doing this, explain
it is solely for the convenience of the users. Again for the full effect,
clone any common logic.


Declare every method and variable public. After all, somebody, sometime
might want to use it. Once a method has been declared public, it can't
very well be retracted, now can it? This makes it very difficult to later
change the way anything works under the covers. It also has the delightful
side effect of obscuring what a class is for. If the boss asks if you are
out of your mind, tell him you are following the classic principles of
transparent interfaces.


In C++, overload library functions by using #define. That way it looks
like you are using a familiar library function where in actuality you are
using something totally different.


In C++, overload +,-,*,/ to do things totally unrelated to addition, subtraction
etc. After all, if the Stroustroup can use the shift operator to do I/O,
why should you not be equally creative? If you overload +, make sure you
do it in a way that
i = i + 5; has a totally different meaning
from i += 5;


When documenting, and you need an arbitrary name to represent a filename
use "file". Never use an obviously arbitrary name like "Charlie.dat"
or
"Frodo.txt". In general, in your examples, use arbitrary names
that sound as much like reserved keywords as possible. For example, good
names for parameters or variables would be: "bank",
"blank",
"class",
"const",
"constant",
"input",
"key",
"keyword",
"kind",
"output",
"parameter""parm",
"system",
"type",
"value",
"var"
and
"variable". If you use actual reserved words for your arbitrary
names, which would be rejected by your command processor or compiler, so
much the better. If you do this well, the users will be hopelessly confused
between reserved keywords and arbitrary names in your example, but you
can look innocent, claiming you did it to help them associate the appropriate
purpose with each variable.


Always document your command syntax with your own, unique, undocumented
brand of BNF notation. Never explain the syntax by providing a suite of
annotated sample valid and invalid commands. That would demonstrate a complete
lack of academic rigour. Railway diagrams are almost as gauche. Make sure
there is no obvious way of telling a terminal symbol (something you would
actually type) from an intermediate one -- something that represents a
phrase in the syntax. Never use typeface, colour, caps, or any other visual
clues to help the reader distinguish the two. Use the exact same punctuation
glyphs in your BNF notation that you use in the command language itself,
so the reader can never tell if a (...), [...], {...} or "..." is something
you actually type as part of the command, or is intended to give clues
about which syntax elements are obligatory, repeatable or optional in your
BNF notation. After all, if they are too stupid to figure out your variant
of BNF, they have no business using your program.


The macro preprocessor offers great opportunities for obfuscation. The
key technique is to nest macro expansions several layers deep so that you
have to discover all the various parts in many different *.hpp files. Placing
executable code into macros then including those macros in every *.cpp
file (even those that never use those macros) will maximize the amount
of recompilation necessary if ever that code changes.


Java is schizophrenic about array declarations. You can do them the old
C, way String x[], (which uses mixed pre-postfix notation) or the new way
String[] x, which uses pure prefix notation. If you want to really confuse
people, mix the notations: e.g.

byte[] rowvector,
colvector, matrix[];
which is equivalent to:
byte[] rowvector;
byte[] colvector;
byte[][] matrix;


Java offers great opportunity for obfuscation whenever you have to convert.
As a simple example, if you have to convert a double to a String, go circuitously,
via Double with new Double(d).toString rather than the more direct
Double.toString(d).
You can, of course, be far more circuitous than that! Avoid any conversion
techniques recommended by the Conversion
Amanuensis. You get bonus points for every extra temporary object you
leave littering the heap after your conversion.


Use threads with abandon.



Philosophy
The people who design languages are the people who write the compilers
and system classes. Quite naturally they design to make their work easy
and mathematically elegant. However, there are 10,000 maintenance programmers
to every compiler writer. The grunt maintenance programmers have absolutely
no say in the design of languages. Yet the total amount of code they write
dwarfs the code in the compilers.
An example of the result of this sort of elitist thinking is the JDBC
interface. It makes life easy for the JDBC implementor, but a nightmare
for the maintenance programmer. It is far
clumsier than the Fortran
interface that came out with SQL three decades ago.
Maintenance programmers, if somebody ever consulted them, would demand
ways to hide the housekeeping details so they could see the forest for
the trees. They would demand all sorts of shortcuts so they would not have
to type so much and so they could see more of the program at once on the
screen. They would complain loudly about the myriad petty time-wasting
tasks the compilers demand of them.
There are some efforts in this direction: NetRexx,
Bali, and visual editors (e.g. IBM's Visual Age
is a start) that can collapse detail irrelevant to the current purpose.

The Shoemaker Has No Shoes
Imagine having an accountant as a client who insisted on maintaining his
general ledgers using a word processor. You would do you best to persuade
him that his data should be structured. He needs validation with cross
field checks. You would persuade him he could do so much more with that
data when stored in a database, including controlled simultaneous update.
Imagine taking on a software developer as a client. He insists on maintaining
all his data with a text editor. He is not yet even exploiting the word
processor's colour, type size or fonts.
Think of what might happen if we started storing source code as structured
data. We could view the same source code in many alternate ways,
e.g. as Java, as NextRex, as a decision table, as a flow chart, as a loop
structure skeleton (with the detail stripped off), as Java with various
levels of detail or comments removed, as Java with highlights on the variables
and method invocations of current interest, or as Java with generated comments
about argument names and/or types. We could display complex arithmetic
expressions in 2D, the way TeX and mathematicians do. You could see code
with additional or fewer parentheses, (depending on
how comfortable you feel with the precedence rules ).
Parenthesis nests could use varying size and colour to help matching by
eye. With changes as transparent overlay sets that you can optionally remove
or apply, you could watch in real time as other programmers on your team,
working in a different country, modified code in classes that you were
working on too.
You could use the full colour abilities of the modern screen to give
subliminal clues, e.g. by automatically assigning a portion of the spectrum
to each package/class using a pastel shades as the backgrounds to any references
to methods or variables of that class. You could bold face the definition
of any identifier to make it stand out.
You could ask what methods/constructors will produce an object of type
X? What methods will accept an object of type X as a parameter? What variables
are accessible in this point in the code? By clicking on a method invocation
or variable reference, you could see its definition, helping sort out which
version of a given method will actually be invoked. You could ask to globally
visit all references to a given method or variable, and tick them off once
each was dealt with. You could do quite a bit of code writing by point
and click.
Some of these ideas would not pan out. But the best way to find out
which would be valuable in practice is to try them. Once we had the basic
tool, we could experiment with hundreds of similar ideas to make like easier
for the maintenance programmer.
I discuss this further under SCID and in the SCID student
project.

Contributors
The following are some of the people who contributed to this list. My lawyers
recommended I exclude those who taught by example.


Hugh McDonald, hughmcd@ican


Gareth Meyrick, gareth@pangloss.ucsf.edu


Jarle Stabell, jarle.stabell@dokpro.uio.no


Ko-Haw Nieh, niko@quality.com


Jim Johnson, jimj@jumpmusic.com


Jim Hyslop, Jim.Hyslop@mars.leitch.com


George Ruban, gruban%adsl4@gte.com


Mats Carlid, mats@adbk.se


John P. McGrath, mcgrath@enter.net


Brian Hurt, brianh@bit3.com


Chris Schlenker, Christoph.Schlenker@gfk.de


Nicholas Widdows, nicholas.widdows@traceplc.co.uk


Greg Compestine, gregcompestine@caleb-bldr.com


Carl L. Gay, sigue@thecia.net

This article appeared in Java Developers' Journal (volume 2 issue 6). I
also spoke on this topic in 1997 November at the Colorado
Summit Conference. It has been gradually growing ever since. I have
had quite a few requests for permission to build links here. You are welcome
to.
If you enjoyed this essay you might like this one on how
to write like a newbie.
 






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