@Override
    public int compare(Object obj1, Object obj2) {
      GlobalTransaction gtx1 = (GlobalTransaction) obj1;
      GlobalTransaction gtx2 = (GlobalTransaction) obj2;
      return gtx1.compare(gtx2);
    }
Sort the array in ascending order of expiration times
geode-core/src/main/java/org/apache/geode/internal/jta/TransactionManagerImpl.java