#fixed code
                              @Override
  public void assign(RingGroup ringGroup, int ringNum, Domain domain) throws IOException {
    ring = ringGroup.getRing(ringNum);
    domainGroup = ringGroup.getDomainGroup();
    domainId = domainGroup.getDomainId(domain.getName());
    version = domainGroup.getLatestVersion().getVersionNumber();
    random = new Random();
    
    for (Host host : ring.getHosts()) {
      if (host.getDomainById(domainId) == null)
        host.addDomain(domainId);
    }

    // make random assignments for any of the currently unassigned parts
    for (Integer partNum : ring.getUnassignedPartitions(domain)) {
      getMinHostDomain().addPartition(partNum, version);
    }

    while (!assignmentsBalanced()) {
      HostDomain maxHostDomain = getMaxHostDomain();
      HostDomain minHostDomain = getMinHostDomain();

      // pick a random partition from the maxHost
      ArrayList<HostDomainPartition> partitions = new ArrayList<HostDomainPartition>();
      partitions.addAll(maxHostDomain.getPartitions());
      final HostDomainPartition toMove = partitions.get(random.nextInt(partitions.size()));

      // assign it to the min host. note that we assign it before we unassign it
      // to ensure that if we fail at this point, we haven't left any parts
      // unassigned.
      minHostDomain.addPartition(toMove.getPartNum(), version);

      // unassign it from the max host
      unassign(toMove);
    }
  }
#vulnerable code 
                              @Override
  public void assign(RingGroup ringGroup, int ringNum, Domain domain) throws IOException {
    ring = ringGroup.getRing(ringNum);
    domainGroup = ringGroup.getDomainGroup();
    domainId = domainGroup.getDomainId(domain.getName());
    version = domainGroup.getLatestVersion().getVersionNumber();
    random = new Random();

    // make random assignments for any of the currently unassigned parts
    for (Integer partNum : ring.getUnassignedPartitions(domain)) {
      getMinHostDomain().addPartition(partNum, version);
    }

    while (!assignmentsBalanced()) {
      HostDomain maxHostDomain = getMaxHostDomain();
      HostDomain minHostDomain = getMinHostDomain();

      // pick a random partition from the maxHost
      ArrayList<HostDomainPartition> partitions = new ArrayList<HostDomainPartition>();
      partitions.addAll(maxHostDomain.getPartitions());
      final HostDomainPartition toMove = partitions.get(random.nextInt(partitions.size()));

      // assign it to the min host. note that we assign it before we unassign it
      // to ensure that if we fail at this point, we haven't left any parts
      // unassigned.
      minHostDomain.addPartition(toMove.getPartNum(), version);

      // unassign it from the max host
      unassign(toMove);
    }
  } 
                            #location 11 
                            #vulnerability type NULL_DEREFERENCE