code: public static Map<Integer, Integer>
              getMapOfContiguousPartitionRunLengths(final Cluster cluster, int zoneId) {
          Map<Integer, Integer> idToRunLength = getMapOfContiguousPartitions(cluster, zoneId);
          Map<Integer, Integer> runLengthToCount = Maps.newHashMap();
  
          if(idToRunLength.isEmpty()) {
              return runLengthToCount;
          }
  
          for(int runLength: idToRunLength.values()) {
              if(!runLengthToCount.containsKey(runLength)) {
                  runLengthToCount.put(runLength, 0);
              }
              runLengthToCount.put(runLength, runLengthToCount.get(runLength) + 1);
          }
  
          return runLengthToCount;
      }
docs: Determines a histogram of contiguous runs of partitions within a zone.
  I.e., for each run length of contiguous partitions, how many such runs
  are there.
  
  Does not correctly address "wrap around" of partition IDs (i.e., the fact
  that partition ID 0 is "next" to partition ID 'max')
  
  @param cluster
  @param zoneId
  @return map of length of contiguous run of partitions to count of number
  of such runs.