Hey I got the answer. Here is the code for getting workspaces for exact owner.It might help someone :)

                     //Set the criteria for workspace
           IWorkspaceSearchCriteria workspaceCriteria = IWorkspaceSearchCriteria.FACTORY.newInstance();
            workspaceCriteria.setKind(IWorkspaceSearchCriteria.WORKSPACES);
         //getting workspaces of exact owner.
            workspaceCriteria.setExactOwnerName(repository.loggedInContributor().getName());
            List<IWorkspaceHandle> workspaceList;
         workspaceList = mgr.findWorkspaces(workspaceCriteria, Integer.MAX_VALUE, null);
         Stream workspaceObj = null;
         @SuppressWarnings("unchecked")

           List<IWorkspace> iWorkspaces = repository.itemManager().fetchCompleteItems(workspaceList,       IItemManager.DEFAULT, null);