Obtaining subcategory using findCategories method

I am implementing an interface for users to open RTC work items.
One part of that interface allows users to select from a list of categories.

I use the following method to obtain that list:

----
public String[] getFiledAgainstList(String projectAreaString, IProgressMonitor monitor) throws TeamRepositoryException {
        String[] fileAgainstList = null;
        IProjectArea projectArea = null;
       
        try {
            projectArea = findProjectAreaByName(projectAreaString);
        } catch (Exception e) {
            MyPlugin.println("Unable to obtain projectArea in getFiledAgainstList:" + e + ":" + e.getMessage());
        }
       
        int i =0;
        try {
            ItemProfile<ICategory> profile= ICategory.DEFAULT_PROFILE.createExtension(ICategory.CATEGORY_ID);
   
            List<ICategory> enumeration = workItemClient.findCategories(projectArea, profile, monitor);
            fileAgainstList = new String[enumeration.size()];
            for (ICategory literal : enumeration) {
                fileAgainstList[i] = literal.getName();
                System.out.println(literal.getName());
                i++;
            }
        }
        catch (TeamRepositoryException e) {
            MyPlugin.println("Unable to obtain profile/enumeration in getFiledAgainstList:" + e + ":" + e.getMessage());
        }
        return fileAgainstList;
    }
-----

We have a set of categories with subcategories as follows.

C1
C2
C3
  C3.S1
  C3.S2
  C3.S3
C4
C5

The code above ends up producing a flat list:

C1
C2
C3
C3.S1
C3.S2
C3.S3
C4
C5

There is no way for me to associate C3.S1 to the C3 category.

In fact what I want is something like:
C1
C2
C3
C3/C3.S1
C3/C3.S2
C3/C3.S3
C4
C5

Otherwise, when I attempt to set the Category using the following method, I get a failure due to the category not being recognized by findCategoryByNamePath.


---
public void setWorkItemCategory(IWorkItem workItemCopy, IProjectArea projectArea, String categoryName) throws TeamRepositoryException
    {
        List<String> path= Arrays.asList(categoryName);
       
        ICategoryHandle category = null;
       
        try {
            category = getWorkItemClient().findCategoryByNamePath(projectArea, path, null);
        }
        catch (Exception e) {
            MyPlugin.println("RTCClient: setWorkItemCategory() - findCategoryByNamePath() failed for categoryName '"+ categoryName + "'!!" + e + ":" + e.getMessage());
            throw new TeamRepositoryException(e);
        }
       
        if (category == null)
        {
            throw new TeamRepositoryException("RTCClient: modifyWorkItemWorkingCopyWithoutSave() - findCategoryByNamePath() failed for categoryName '"+ categoryName + "'!!");
        }
       
        workItemCopy.setCategory(category);
    }
---

Is there any way to accomplish what I described above?