Map as a return value? 2004-01-27 - By Erik Beijnoff
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Pardon me if you find this question to common to fit into the j2ee
category.
I suppose this question is impossible to answer with a simple yes or no,
but I'm looking for standard practices when an object deals with
collections as return values from a method invocation.
Say that I call some getParameters() method on some object that returns
a Map of parameters. Should the Map be copied before it is returned so
that the calling object can't affect the original Map, or should the Map
be returned by reference?
My spontaneous feeling is that the object shouldn't spill it's internal
guts around, so the Map should really be a copy of the other Map, but
what about performance if you have to create and recreate copies of all
Maps that gets passed around the system?
What are the situations where it is acceptable, or even wanted for an
object to return a shared Map? Or do you find it acceptable, from a
performance point of view to hand out the Map as long as you "know" that
you will only read the Map?
I know that there are different situation where different rules apply,
of course, but what I'm looking for is what these different situations
really are. I've found my self contemplating this implementation detail
quite often recently, and often tended to go with the shared object
approach, propably out of scare to affect performance.
Regards Erik Beijnoff
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<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>Pardon me if you
find this question to common to fit into the j2ee category.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=757104809-27012004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>I suppose this
question is impossible to answer with a simple yes or no, but I'm looking for
standard practices when an object deals with collections as return values
from a method invocation.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=757104809-27012004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>Say that I call
some
getParameters() method on some object that returns a Map of parameters. Should
the Map be copied before it is returned so that the calling object can't affect
the original Map, or should the Map be returned by
reference?</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=757104809-27012004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>My spontaneous
feeling is that the object shouldn't spill it's internal guts around, so the
Map
should really be a copy of the other Map, but what about performance if you
have
to create and recreate copies of all Maps that gets passed around the
system?</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=757104809-27012004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>What are the
situations where it is acceptable, or even wanted for an object to return
a
shared Map? Or do you find it acceptable, from a performance point of view to
hand out the Map as long as you "know" that you will only read the
Map?</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=757104809-27012004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>I know that there
are different situation where different rules apply, of course, but what I'm
looking for is what these different situations really are. I've found my self
contemplating this implementation detail quite often recently, and often tended
to go with the shared object approach, propably out of scare to affect
performance. </SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=757104809-27012004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=757104809-27012004>Regards Erik
Beijnoff</SPAN></FONT></DIV></BODY></HTML>
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To unsubscribe, send email to listserv@(protected) and include in the body
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