Re: Declaring outside a loop: speed? memory?
- From: "Steve W. Jackson" <stevewjackson@xxxxxxxxxxx>
- Date: Tue, 23 Jan 2007 10:50:42 -0600
In article
<45b5fbb5$0$7993$5a62ac22@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Ben Caradoc-Davies <ben@xxxxxxxxxxxxx> wrote:
Philipp wrote:
Just wondering, is there a speed or memory difference between the two
following codes?
Funny you should ask, because it was just mentioned on Planet Classpath
http://planet.classpath.org/
Local Variables in Java
http://rmathew.blogspot.com/2007/01/local-variables-in-java.html
In short, there is no difference. The JVM specification requires them to
be the same, and the same bytecode is generated.
Given the specific code sample cited, I don't think there's enough
information to say that with certainty. Since it was omitted from the
reply, I'll paste it here:
--- code ---
for(int i = 0; i < 1000; i++){
MyClass mine = new MyClass();
mine.doSomething();
}
------------
and
--- code ---
MyClass mine;
for(int i = 0; i < 1000; i++){
mine = new MyClass();
mine.doSomething();
}
------------
In terms of speed, yes, it should be the same. In terms of memory,
there may be a difference depending on what else might follow the loop
in the second snippet.
Declaring the variable "mine" before the loop makes its scope wider than
just the loop. As a result, the last instance after the loop terminates
is still in existence until the wider scope is finished. Only then is
it certain to be eligible for garbage collection, should the JVM need to
do so. So if there's a good deal that follows this loop, there could be
a benefit to the first approach.
Personally, I would tend (in situations like this one) to opt for a form
slightly more compact than that inside the loop:
new MyClass().doSomething();
= Steve =
--
Steve W. Jackson
Montgomery, Alabama
.
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