Get All the Child Organizations of a given Organization including sub hierarchies

public static List getChildorganizations(String orgkey) {

             List<String> childOrgList = new ArrayList<>();

             RoleManager roleMgr = oimClient.getService(RoleManager.class);

             tcAccessPolicyOperationsIntf accessPolicyIntf = oimClient.getService(tcAccessPolicyOperationsIntf.class);

             ApplicationInstanceService AppInstSer = oimClient.getService(ApplicationInstanceService.class);

             EntityPublicationService entityPubService = oimClient.getService(EntityPublicationService.class);

             OrganizationManager orgManager = oimClient.getService(OrganizationManager.class);

             try {

                    HashMap<String, Object> configParams = new HashMap<String, Object>();

                    Set<String> retAttrs = new HashSet<String>();

                    List<Organization> ChildOrg = new ArrayList<Organization>();

                    ChildOrg = orgManager.getChildOrganizations(orgkey, retAttrs, configParams);

                    System.out.println("Child Organizations Details : " + ChildOrg);

                    if (ChildOrg != null) {

                           for (int s = 0; s < ChildOrg.size(); s++) {

                                 String childorgkey = ChildOrg.get(s).getEntityId();

                                 System.out.println("Child Org Key : " + childorgkey);

                                 childOrgList.add(childorgkey);

                                 // System.out.println("Child Org List : " +childOrgList);

                                 List<Organization> grandChildOrg = new ArrayList<Organization>();

                                 grandChildOrg = orgManager.getChildOrganizations(childorgkey, retAttrs, configParams);

                                 if (grandChildOrg != null) {

                                        for (int a = 0; a < grandChildOrg.size(); a++) {

                                               String grandchildorgkey = grandChildOrg.get(a).getEntityId();

                                               System.out.println("Grand Child Org Key : " + grandchildorgkey);

                                               childOrgList.add(grandchildorgkey);

                                               List<Organization> garndgrandChildOrg = new ArrayList<Organization>();

                                               garndgrandChildOrg = orgManager.getChildOrganizations(grandchildorgkey, retAttrs,

                                                            configParams);

                                               if (garndgrandChildOrg != null) {

                                                     for (int b = 0; b < garndgrandChildOrg.size(); b++) {

                                                            String garndgrandchildorgkey =garndgrandChildOrg.get(b).getEntityId();

                                                            System.out.println("Grand Grand Child Org Key : " +garndgrandchildorgkey);

                                                            childOrgList.add(garndgrandchildorgkey);

                                                     }

                                               }

                                        }

                                 }

                           }

                    }

                    System.out.println("Child Org List outside while: " + childOrgList);

             } catch (Exception e) {

                    e.printStackTrace();

             }

             return childOrgList;

       }