Index: sources/org/apache/batik/util/CleanerThread.java
===================================================================
--- sources/org/apache/batik/util/CleanerThread.java	(revision 911532)
+++ sources/org/apache/batik/util/CleanerThread.java	(working copy)
@@ -34,17 +34,10 @@
  */
 public class CleanerThread extends Thread {
 
-    static volatile ReferenceQueue queue = null;
-    static CleanerThread  thread = null;
-
-    public static ReferenceQueue getReferenceQueue() {
+    volatile ReferenceQueue<Object> queue;
+    public static final CleanerThread  THREAD = new CleanerThread();
 
-        if ( queue == null ) {
-            synchronized (CleanerThread.class) {
-                queue = new ReferenceQueue();
-                thread = new CleanerThread();
-            }
-        }
+    public synchronized ReferenceQueue<Object> getReferenceQueue() {
         return queue;
     }
 
@@ -65,7 +58,7 @@
     public abstract static class SoftReferenceCleared extends SoftReference
       implements ReferenceCleared {
         public SoftReferenceCleared(Object o) {
-            super (o, CleanerThread.getReferenceQueue());
+            super (o, THREAD.getReferenceQueue());
         }
     }
 
@@ -76,7 +69,7 @@
     public abstract static class WeakReferenceCleared extends WeakReference
       implements ReferenceCleared {
         public WeakReferenceCleared(Object o) {
-            super (o, CleanerThread.getReferenceQueue());
+            super (o, THREAD.getReferenceQueue());
         }
     }
 
@@ -88,22 +81,24 @@
         extends PhantomReference
         implements ReferenceCleared {
         public PhantomReferenceCleared(Object o) {
-            super (o, CleanerThread.getReferenceQueue());
+            super (o, THREAD.getReferenceQueue());
         }
     }
 
     protected CleanerThread() {
         super("Batik CleanerThread");
+        queue = new ReferenceQueue<Object>();
         setDaemon(true);
         start();
     }
 
     public void run() {
-        while(true) {
+    	ReferenceQueue<Object> rq;
+        while ((rq = getReferenceQueue ()) != null) {
             try {
                 Reference ref;
                 try {
-                    ref = queue.remove();
+                    ref = rq.remove();
                     // System.err.println("Cleaned: " + ref);
                 } catch (InterruptedException ie) {
                     continue;
@@ -120,4 +115,24 @@
             }
         }
     }
+    
+    /**
+     * Stops the cleaner thread. Calling this method is recommended in all long running applications
+     * with custom class loaders (e.g., web applications).
+     */
+    public void exit() {
+        // try to stop it gracefully
+        synchronized (this) {
+            queue = null;
+        }
+        this.interrupt();
+        try {
+            this.join(500);
+        } catch (InterruptedException e) {
+
+        }
+        // last resort tentative to kill the cleaner thread
+        if (this.isAlive())
+            this.stop();
+    }
 }