private int getWeight(Collection<ID> idms,
      MemberIdentifier leader) {
    int weight = 0;
    for (ID mbr : idms) {
      int thisWeight = mbr.getMemberWeight();
      if (mbr.getVmKind() == 10 /* NORMAL_DM_KIND */) {
        thisWeight += 10;
        if (leader != null && mbr.equals(leader)) {
          thisWeight += 5;
        }
      } else if (mbr.preferredForCoordinator()) {
        thisWeight += 3;
      }
      weight += thisWeight;
    }
    return weight;
  }
GMSQuorumChecker is the implementation of QuorumChecker and can be used to determine
whether a quorum of membership is accessible.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/messenger/GMSQuorumChecker.java