private static List<Integer> sortedPorts(int n) {
    List<Integer> ports = new ArrayList<>(n);
    for (int i = 0; i < n; ++i) {
      ports.add(HBaseTestingUtil.randomFreePort());
    }
    Collections.sort(ports);
    return ports;
  }
Generates a list of random port numbers in the sorted order. A sorted order makes sense if we
ever want to refer to these servers by their index in the returned array, e.g. server #0, #1,
etc.
hbase-diagnostics/src/test/java/org/apache/hadoop/hbase/util/ProcessBasedLocalHBaseCluster.java