Trip Discovery - Mapper reads CSV data format

TripCellMapper.java

public class TripCellMap extends Mapper<LongWritable, Text, Text, CarSortWritable> {

    // column indices for values in the vehicle CSV
    static final int COL_CAR = 0;  // vehicle ID
    static final int COL_DAT = 1;  // date in YYMMDD
    static final int COL_TIM = 2;  // time in HHMMSS
    static final int COL_LON = 3;  // longitude in DMS
    static final int COL_LAT = 4;  // latitude in DMS
    static final int COL_DIR = 5;  // compass orientation in degrees
    static final int COL_SPD = 6;  // speed in km/h
    static final int COL_ROD = 7;  // road type code

    @Override
    public void map(LongWritable key, Text val, Context context)
            throws IOException, InterruptedException {

        /* 
         * The TextInputFormat we set in the configuration, splits a text file line by line.
         * The key is the byte offset to the first character in the line.  The value is the text of the line.
         */
        
        // Note: no header row in this CSV

        String line = val.toString();
        String[] values = line.split(",");  // no comma in quoted string in input
        Text key2 = new Text(values[COL_CAR] + "," + values[COL_DAT]);
        CarSortWritable data = new CarSortWritable(values[COL_DAT], values[COL_TIM],
                                                   values[COL_LON], values[COL_LAT],
                                                   values[COL_DIR], values[COL_SPD], values[COL_ROD]);
        context.write(key2, data);

    }

}