public void setDefaultClientPort(int clientPort) {
    if (clientPort <= 0) {
      throw new IllegalArgumentException("Invalid default ZK client port: " + clientPort);
    }
    this.defaultClientPort = clientPort;
  }
Check whether the client port in a specific position of the client port list is valid.
@param index the specified position
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/MiniZooKeeperCluster.java