Sometimes I see this stacktrace in javamelody:

ajp-apr-8009-exec-40
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281)
java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:218)
java.util.concurrent.FutureTask.get(FutureTask.java:83)
org.icepdf.core.pobjects.graphics.ImageReference.createImage(ImageReference.java:107)
org.icepdf.core.pobjects.graphics.CachedImageReference.getImage(CachedImageReference.java:55)
org.icepdf.core.pobjects.graphics.ImageReference.drawImage(ImageReference.java:71)
org.icepdf.core.pobjects.graphics.commands.ImageDrawCmd.paintOperand(ImageDrawCmd.java:50)
org.icepdf.core.pobjects.graphics.Shapes.paint(Shapes.java:136)
org.icepdf.core.pobjects.Page.paintPageContent(Page.java:543)
org.icepdf.core.pobjects.Page.paint(Page.java:500)
org.icepdf.core.pobjects.Page.paint(Page.java:432)
org.icepdf.core.pobjects.Document.getPageImage(Document.java:1097)

What could be the problem? The code is:

byte[][] data = new byte[end - start + 1][];
        try {
            int index = 0;
            for (int i = start - 1; i < end; i++) {
                baous = new ByteArrayOutputStream();
                image = (BufferedImage) document.getPageImage(
                        i, GraphicsRenderingHints.PRINT, Page.BOUNDARY_CROPBOX, 0, scale);
                ImageIO.write(image, "png", baous);
                data[index] = baous.toByteArray();
                index++;
                image.flush();
                image = null;
                baous.flush();
                baous.close();
            }
        } finally {
            document.dispose();
        }