Re: Avoid creating a stacktrace prior to JDK 1.7
Jan Burse wrote:
Lew schrieb:
in the first place.
/Effective Java/, Joshua Bloch, "Item 57: Use exceptions only for except=
ional conditions".
The JDK itself violates this rule. For example
each time a Thread is created the following
check is run:
... [snip excellent example] ...
In the above the sunshine flow is that we get a boolean
value false, which means that two NoSuchMethodExceptions
are thrown. It seems that in connection with the reflection
API using the exceptions for business logic has become
the prefered idiom contrary to the advice.
But this is probably due to a lack of a better reflection
API. Or we can even analysis it deeper. Since the reflection
API methods can return so much information AND since java
does not have multi valued returns, the exceptions have
been abused for returning additional information.
In the Go Programming language one would do something:
getDeclaredMethod(String,Class[]) (Method,Error)
Shit happens!
P.S.: Actually the situation is worse in JDK 1.7, the
audit is done but then cached during the call of
isCCLOverridden(). This is good. But each call of
isCCLOverridden() does also poll the cache for
removal of inaccessible keys! Hm, not sure what
I should think about that.
Excellent analysis and conclusions.
In bringing up the rule "Use exceptions only for exceptional conditions" [/=
op cit./] I omitted to mention another important rule, or set of rules:
- There are no universal rules.
and its corollaries/consequents,
- Rules were made to be broken.
- The virtuoso knows when to break the rules. (The master creates the rule=
s.)
- The exception probes the rule. [original intent of the clich=E9 preserve=
d]
Like all the engineering decisions we make, the use of exceptions balances =
alternatives. One could argue that the conditions you showed in your examp=
le were "exceptional" enough to merit handling by exception. Pragmatically=
, the alternatives suck by comparison anyway. Y'know, that motivating "exc=
eptional conditions" clause leaves a whole lotta wiggle room.
It's a common joke in engineering disciplines to issue harsh directives tha=
t boil down to, "Do what thou wilt, but use good judgment." This does not =
detract from the wisdom of the advice.
--
Lew