How to revise WTPartDescribeLink

I have WTPart object with describe links WTDocuments associated with that.Now I need to revise the PartDescribeLink through code.

Below is the code I have tried so far..

Vector localVector=new Vector();

QueryResult localQueryResult=WTPartHelper.service.getDescribedByWTDocuments(part,false);

System.out.println("size is "+localQueryResult.size());

                    if((localQueryResult!=null)&&(localQueryResult.hasMoreElements()))

                    {

                              while(localQueryResult.hasMoreElements())

                              {

     WTObject localObject=(WTObject) localQueryResult.nextElement();

      localVector.addElement(localObject);

                              }

                    }

                    if((localVector!=null)&&(localVector.size()>0))

                    {

                              for(int i=0;i<localVector.size();i++)

                              {

                                        WTPartDescribeLink localPartlink=(WTPartDescribeLink) localVector.elementAt(i);

   WTDocument localWTDocument=localPartlink.getDescribedBy();

   System.out.println("values are "+localWTDocument.getNumber());

                                        RevisionControlled localRevisionControlled=null;

                                        localRevisionControlled=(RevisionControlled) VersionControlHelper.service.newVersion(localWTDocument);

                                        localRevisionControlled=(RevisionControlled) PersistenceHelper.manager.save(localRevisionControlled);

}

                    }

This code is revising only the WTDocument object but not the partDescribelink.If I tried to pass the Describelink object directly like this

localRevisionControlled=(RevisionControlled) VersionControlHelper.service.newVersion((Versioned)localPartlink);

means it is showing the following error message.

Exception in thread "main" java.lang.ClassCastException: wt.part.WTPartDescribeLink cannot be cast to wt.vc.Versioned

          at ext.gt.test.CheckLink.getPartlink(CheckLink.java:94)

          at ext.gt.test.CheckLink.searchPart(CheckLink.java:52)

          at ext.gt.test.CheckLink.main(CheckLink.java:32)

I need to revise the link in code.Someone help me with giving the API or some example code snippets would be helpful for me.

Thank you