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Fail Early, Fail Often
JavaFAQ Home » Java Notes by Fred Swartz
You will write bugs
In programming you will write a lot of bugs. Just accept it. I've known a lot of
fantatically capable programmers, but only one who wrote essentially flawless
code in the first draft, Ira Rubin.
Mistakes are educational
If you aren't writing bugs, at least while you're still learning the art of
programming, you probably aren't pushing yourself to try new things. You can
rationalize a lot of errors by repeating "I learn more from my mistakes than my
successes", and it's probably true.
Compile-time errors are the best
Ideally, you want someone else to find your errors. Compiler error checking is
your friend because it finds errors you've made immediately and tells you about
them. Some development systems even have continuous compilation, so you are
informed about errors during compilation. I haven't tried these systems, but
imagine it might work something like spelling checkers that put a read line
under words that might be errorneous as you type -- not intrusive, but letting
you know where there may be a problem.
The quality of compile-time error diagnosis is both a function of language
design and the compiler design. The Java language is so-so in this area, however
its strong typing (variable types must be declared) and required casting
are very good features. Some of the rumored featuers of JDK 1.5 will further
improve compile time checks, eg, templates, type-safe enums, and a "foreach"
statement. The goal of not allowing illegal programs to compile is impossible,
but its always interesting to think of how the language design could be improved
to help detect errors at compile time.
Catch runtime errors early if possible
The worst kind of runtime error causes the program to slowly fall apart. Perhaps
the greated leap that Java made over C++ is in providing runtime checks that
various common errors. Perhaps the most important features are garbage
collection and array indexes out of range.
Yet, there are still many possible run-time errors. Java provides another
great tool in the
assert statement which checks that things
that must be true really are (See Assertions). Learn about assertions and use
While it is true that testing can only show the presence of bugs, not their
absence, it essential. Methodologies such as Extreme Programming require
that test data be written before the code. The
facility makes writing and running tests much easier. With fast machines it is
possible to run regression tests frequently. See Testing.
Fail early, fail often
You will write bugs and you want them caught as early as possible. Use types to
help catch errors at compile time if possible; use assertions to stop execution
if something is wrong; use rigorous testing to find errors.
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