question: private void extractRowKeyAndData ( String line , DefaultCategoryDataset dataset , List columnKeys ) { Comparable rowKey = null ; int fieldIndex = 0 ; int start = 0 ; for ( int i = 0 ; i < line . length ( ) ; i ++ ) { if ( line . charAt ( i ) == this . fieldDelimiter ) { if ( fieldIndex == 0 ) { String key = line . substring ( start , i ) ; rowKey = removeStringDelimiters ( key ) ; } else { Double value = Double . valueOf ( removeStringDelimiters ( line . substring ( start , i ) ) ) ; dataset . addValue ( value , rowKey , ( Comparable ) columnKeys . get ( fieldIndex - 1 ) ) ; } start = i + 1 ; fieldIndex ++ ; } } Double value = Double . valueOf ( removeStringDelimiters ( line . substring ( start , line . length ( ) ) ) ) ; dataset . addValue ( value , rowKey , ( Comparable ) columnKeys . get ( fieldIndex - 1 ) ) ; }
target:  Extracts the row key and data for a single line from the input source.