OK.
I have the following document loaded in memory as a DOM:
<root>
<a_node>
<some_node>
<child>
...
</child>
</some_node>
</a_node>
...
</root>
and repeatedly want to clone <some_node> in order to manipulate
it, but keep the original node. Shouldn't the memory be reclaimed
in the code in my original example?
I have attached an example (as text files for your convenience)
illustrating my problem. The output is as follows:
Memory usage after 0 clones: 2204464
Memory usage after 1000 clones: 2853408
Memory usage after 2000 clones: 3501408
Memory usage after 3000 clones: 4149408
Memory usage after 4000 clones: 4797408
Memory usage after 5000 clones: 5445408
Memory usage after 6000 clones: 6093408
Memory usage after 7000 clones: 6741408
Memory usage after 8000 clones: 7389408
Memory usage after 9000 clones: 8037408
Memory usage after 10000 clones: 8685408
The forced garbage collecting does not do affect the
result noticeably. Setting the cloned node to null
does nothing.
If this is the correct behavior, how can I delete
the cloned node when I do not need it anymore?
/Christian
Andy Clark wrote:
>
> Christian Lizell wrote:
> > Is it the correct behavior that the following statement
> > is not releasing the memory for the cloned node?
> >
> > Node clonedNode = someNode.cloneNode(true);
> > clonedNode = null;
>
> Unless the cloned node is actually a child node in the
> document, the cloned node can be reclaimed. Even though
> the cloned node has a link to the document, what is
> important is the objects that have links to the cloned
> node. If noone references it, then it can be reclaimed.import org.w3c.dom.*;
import org.apache.xerces.parsers.DOMParser;
public class CloneTest {
public static void main(String[] args) {
// Parse the document
DOMParser parser = new DOMParser();
try {
parser.parse("clonetest.xml");
}
catch (Exception e) {
e.printStackTrace();
System.exit(0);
}
// Get some_node
Node someNode = null;
try {
someNode =
parser.getDocument().getElementsByTagName("some_node").item(0);
} catch (Exception e) {
e.printStackTrace();
System.exit(0);
}
parser = null; // Just in case
// Make clones
for (int i=0; i<=10000; i++) {
Node clonedNode = someNode.cloneNode(true);
clonedNode = null;
if ((i%1000) == 0) {
System.gc(); System.runFinalization();
Runtime rt = Runtime.getRuntime();
System.out.println("Memory usage after " + i + " clones: " +
(rt.totalMemory()-rt.freeMemory()));
}
}
}
}
<?xml version="1.0" encoding="ISO-8859-1" standalone="yes"?>
<root>
<a_node>
<some_node>
<child>
blah
</child>
</some_node>
</a_node>
</root>
