xml child not deleted

I have a XML as given below. I want to recursively delete the empty tags from the same. As in once f gets deleted e should be deleted and as e gets deleted d is empty and hence that should also be deleted.

<Test>
  <a>test</a>
  <b>test</b>
  <c></c>
     <d>
        <e>
           <f> </f>
        </e>
     </d>
</Test>

result should be

<Test>
  <a>test</a>
  <b>test</b>
</Test>

I am able to delete tag but i am not able to delete tag as it has blank space. Altough I am able to identify this as a tag to be deleted but when I invoke the removeChild() on its parent it is not getting removed from the XML. In the code while debugging it shows the number of child of e after invoking removeChild() as zero. But still it remains in the xml??

Please can you help me what am I doing wrong.

Please find below my code which I am using.

for (Element childElement : toRemove) {
        Node parentNode = childElement.getParentNode();
        System.out.println("Removing null or empty node :: " + childElement.getNodeName());

        if(parentNode!=null){
            NodeList childList = parentNode.getChildNodes();
            System.out.println("List of Childer before deleting :: " + childList.getLength());

            //childElement.setNodeValue(null);

            parentNode.removeChild(childElement);
            clean(parentNode);

            childList = parentNode.getChildNodes();
            int childCount = childList.getLength();

            for (int i = 0; i < childCount; i++) {
                Node childNode = childList.item(i);
                System.out.println("Childs :: " + childNode);
            }

            for (int i = 0; i < childCount; i++) {
                Node childNode = childList.item(i);
                if(childNode!=null){
                    System.out.println("Child before deleting :: " + childNode);

                    if (childNode instanceof Element == false){
                        if(childNode.getNodeValue().trim().isEmpty()){
                            System.out.println("found unwanted :: " + childNode.getNodeName());

                            parentNode.removeChild(childNode);
                            i--;
                            childCount--;
                            clean(parentNode);
                        }
                    }
                }
            }

            childList = parentNode.getChildNodes();
            System.out.println("List of Childer after deleting :: " + childList.getLength());
        }

        /*if(!parentNode.hasChildNodes()){
            parentNodes.add((Element)parentNode);
        }*/
    }