question: public static void writeWritablesToFile ( String outputPath , String delim , List < List < Writable > > writables , JavaSparkContext sc ) throws IOException { StringBuilder sb = new StringBuilder ( ) ; for ( List < Writable > list : writables ) { boolean first = true ; for ( Writable w : list ) { sb . append ( w . toString ( ) ) ; if ( ! first ) sb . append ( delim ) ; first = false ; } sb . append ( "\n" ) ; } writeStringToFile ( outputPath , sb . toString ( ) , sc ) ; }
target:  Wlite a set of writables (or, sequence) to HDFS (or, locally).