URL class is not being garbage collected

Question

I have created two instances of the URL class to specify a file location for each image. I use com.symantec.itools.javax.swing.icons.ImageIcon class to display images specified by each URL instance as icons inside a button. The setImageLocation method(URL location) of the ImageIcon class sets the location to be displayed by this icon. The following is the code snippets used to create the ImageIcon instances:
private URL greenIconURL;
private URL redIconURL;
com.symantec.itools.javax.swing.icons.ImageIcon green_icon = new com.symantec.itools.javax.swing.icons.ImageIcon();
com.symantec.itools.javax.swing.icons.ImageIcon red_icon = new com.symantec.itools.javax.swing.icons.ImageIcon();
try
greenIconURL = new java.net.URL
("file:./images/greenline.gif");
green_icon.setImageLocation(greenIconURL);
catch (java.net.MalformedURLException error) { }
try
redIconURL = new java.net.URL
("file:./images/redline.gif");
red_icon.setImageLocation(redIconURL);
catch (java.net.MalformedURLException error) { }
I am using JProbe 5.0.1 Memory to determine the loitering objects when I remove the button from the JInternalFrame. I am using Java 1.2.2_08 version. The JProbe Memory Leak Doctor indicates that each URL instance has a reference to an entry in a HashMap table. The reference graph from the root set has a reference to SoftCache to HashMap to HashMap$Entry. To make this URL instance eligible for garbage collection, JProbe Memory Leak Doctor indicates I must remove the entry from the HashMap. How do I get access to this HashMap to remove the entry? If this is a problem with the version of the JDK, please let me know. Thank you in advance for your assistance.

Answer 1

<root>Statics
-->sun.misc.SoftCache->java.util.HashMap->java.util.Has
Map$Entry[]->java.util.HashMap$Entry->java.net.URL
I do not an instance of HashMap in my class.
Therefore, the HashMap is either created by URLclass
or the
com.symantec.itools.javax.swing.icons.ImageIcon
class.SoftCache seems to have a normal HashMap inside
it/* Hash table mapping keys to ValueCells */
private Map hash;but if that is the HashMap in JProbe
information then the URL would have to be a key in
the map - otherwise there'd be another object in the
chain of class SoftCache.ValueCell
are you certain that the java.net.URL's in that
hashmap are your ones?
out of curiosity - are you certain that the URL's are
the/a problem (are you getting an OutOfMemoryError?)
asjfThe button that contains the URL's is the only one on the JInternalFrame. The JProbe Memory Debugger displays the java.net package name, the URL class name, the count (2), and the Count Change (+2). When I remove the button from the JInternalFrame, the aforementioned numbers on the Instance Summary remain the same. The snapshot of the Java Heap reveals that the two instances of the URL class are still there. The Memory Leak Doctor shows the reference graph from the root set:
<root>Statics->SoftCache->HashMap->HashMap$Entry[]->HashMap$Entry->URL
When I right click on the arrow between HashMap$Entry[] and HashMap$Entry to remove the reference, I receive the message: "Congratulations this object can be garbage collected..." It appears like private instance of Map in SoftCache is holding a strong reference.
I am not getting an OutOfMemoryError exception.