#fixed code
                              private boolean isBalanced(Ring ring, Domain domain) throws IOException {
    HostDomain maxHostDomain = getMaxHostDomain(ring, domain);
    HostDomain minHostDomain = getMinHostDomain(ring, domain);
    if (maxHostDomain == null || minHostDomain == null) {
      // If either maxHostDomain or minHostDomain is null, the domain is not balanced
      return false;
    }
    int maxDistance = Math.abs(maxHostDomain.getPartitions().size() - minHostDomain.getPartitions().size());
    return maxDistance <= 1;
  }
#vulnerable code 
                              private boolean isBalanced(Ring ring, Domain domain) throws IOException {
    HostDomain maxHostDomain = getMaxHostDomain(ring, domain);
    HostDomain minHostDomain = getMinHostDomain(ring, domain);
    int maxDistance = Math.abs(maxHostDomain.getPartitions().size()
        - minHostDomain.getPartitions().size());
    return maxDistance <= 1;
  } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE