I guess the following code will help you,
AuthorityFilter filter = new AuthorityFilter("GROUP", false);
String[] group = accessControlService.getAllAuthorities(filter);
for (int i = 0; i < group.length; i++) {
System.out.println("result : " + group);
SiblingAuthorityFilter filter1 = new SiblingAuthorityFilter("USER", false);
String[] users = accessControlService.getChildAuthorities(group, filter1);
if(users != null)
for (int j = 0; j < users.length; j++)
System.out.println("users : " + users[j]);
}
Regards,
Madhu