private int compareDegrees(final OutboundMobilityCandidacyContest o) {
   return executionDegreesCompareHash(
           o.getOutboundMobilityCandidacyContestGroup().getExecutionDegreeSet())
       .compareTo(
           executionDegreesCompareHash(
               getOutboundMobilityCandidacyContestGroup().getExecutionDegreeSet()));
 }