public KafkaCluster usingDirectory(File dataDir){
  if (running)   throw new IllegalStateException("Unable to add a broker when the cluster is already running");
  if (dataDir != null && dataDir.exists() && !dataDir.isDirectory() && !dataDir.canWrite() && !dataDir.canRead()) {
    throw new IllegalArgumentException("The directory must be readable and writable");
  }
  this.dataDir=dataDir;
  return this;
}

public KafkaCluster usingDirectory ( File dataDir ) { if ( running ) throw new IllegalStateException ( "Unable to add a broker when the cluster is already running" ) ; if ( dataDir != null && dataDir . exists ( ) && ! dataDir . isDirectory ( ) && ! dataDir . canWrite ( ) && ! dataDir . canRead ( ) ) { throw new IllegalArgumentException ( "The directory must be readable and writable" ) ; } this . dataDir = dataDir ; return this ; }
set the parent directory where the brokers logs and server ' s logs and snapshots will be kept .
