question: public DoubleVector buildVector ( Collection < String > articleTokens , DoubleVector documentVector ) { Map < String , Integer > termCounts = new HashMap < String , Integer > ( ) ; for ( String term : articleTokens ) { Integer count = termCounts . get ( term ) ; termCounts . put ( term , ( count == null || ! useTermFreq ) ? 1 : count . intValue ( ) + 1 ) ; } for ( Map . Entry < String , Integer > entry : termCounts . entrySet ( ) ) { Vector termVector = sspace . getVector ( entry . getKey ( ) ) ; if ( termVector == null ) { continue ; } add ( documentVector , termVector , entry . getValue ( ) ) ; } return documentVector ; }
target:  Represent a document as the summation of term Vectors.