question: protected String concatFields ( SolrInputDocument doc ) { StringBuilder sb = new StringBuilder ( getExpectedSize ( doc , inputFields ) ) ; for ( String fieldName : inputFields ) { log . debug ( "Appending field " + fieldName ) ; if ( doc . containsKey ( fieldName ) ) { Collection < Object > fieldValues = doc . getFieldValues ( fieldName ) ; if ( fieldValues != null ) { for ( Object content : fieldValues ) { if ( content instanceof String ) { String stringContent = ( String ) content ; if ( stringContent . length ( ) > maxFieldValueChars ) { sb . append ( stringContent . substring ( 0 , maxFieldValueChars ) ) ; } else { sb . append ( stringContent ) ; } sb . append ( " " ) ; if ( sb . length ( ) > maxTotalChars ) { sb . setLength ( maxTotalChars ) ; break ; } } else { log . warn ( "Field " + fieldName + " not a String value, not including in detection" ) ; } } } } } return sb . toString ( ) ; }
target:  Concatenates content from multiple fields