Comments on: The Dangers of String.substring

By: Ray

Ray — Tue, 26 Jul 2011 13:39:05 +0000

I agree, I run some performance and tracing the JVM leak before and because the application has a lot of string handling, it points to substring, + and split problem. I tried to create an object to have a pointer in it and it all solve the problem but it requires time to scout all the code that uses it. Very nice notes…

By: JustSomeGuy

JustSomeGuy — Mon, 08 Nov 2010 02:57:51 +0000

This is **not** a bug, it’s a deliberate design decision. A bug is when something doesn’t work to the specification. If you can point me to the docs stating that strings should free up their unused portions, I’ll defer. Until then, it’s a feature request on your part.

By: JavaBlogging » String and memory leaks

JavaBlogging » String and memory leaks — Tue, 28 Jul 2009 11:50:31 +0000

[...] post is inspired by an entry on nflath.com about the dangers of String.substring() [...]

By: Terry

Terry — Tue, 07 Jul 2009 14:17:57 +0000

I don’t understand why this bug is still lurking in Java. Java has been open sourced correct? So someone should be able to go in and change the behavior of the C++ code in the JVM that’s causing this issue. Right?

By: admin

admin — Mon, 06 Jul 2009 21:17:10 +0000

Salman:
You have to wrap the elements of the array that you want to keep, so something like:

String[] items = oldString.split(" ");
String stringToKeep = new String(items[0]);

Will allow the original string to be garbage collected.

By: Salman Ahmed

Salman Ahmed — Mon, 06 Jul 2009 19:44:05 +0000

So, String.split() also leaks memory? What workaround would you recommend for the case when String.split() is used?

By: ghettoimp

ghettoimp — Mon, 06 Jul 2009 02:48:08 +0000

@SJS: It seems unlikely that Andrew’s solution would have any impact on GC performance.

Instead, his proposal is merely for the JVM to attempt a more aggressive recovery strategy before dying with an OutOfMemoryError. It’s true that in such a case, one might reasonably expect the JVM to run its garbage collector to try to find some memory that can be freed. But during any “ordinary” run of the garbage collector, there is still plenty of memory available, and so the “last ditch effort” that Andrew describes (looking for some strings to free) would simply not be invoked.

Andrew’s solution seems fairly reasonable. Ask yourself: would you rather that your program immediately die with an OutOfMemoryError, or that the JVM spends some time in a search for additional memory before it gives up? To me, it seems better to win some of the time than to lose all of the time.

By: Brian

Brian — Mon, 06 Jul 2009 00:34:40 +0000

Actually, you split with a regex that ignores commas inside of quotes. You don’t just split with “,”.

By: Nick

Nick — Sun, 05 Jul 2009 23:18:07 +0000

If you’re parsing CSV by calling String.split you’re doing it wrong anyway.

Foo,”Baz,Baz”,Qux

By: Chris

Chris — Sun, 05 Jul 2009 21:28:42 +0000

@Mark

> Variables should default to string type too
WTF are you smoking? How about real type inference, rather than picking one type and raising it up above the others?