0x001F - Java CSV Parser Example

In this case we have built a CSV reader to read 1 minute data from a file:

• Starting offset is set by int startat,
• CSV files may return extra/empy row sets. These are filtered for in the while (line != null)
• String G[] creates a string array from the line.split(",")
• Java does not have structs similar to C++, instead for each object we create a sub-class at the bottom with a initializer public Quote(float open, float high, float low, float close, float volw, float vol, long ntrades, LocalDateTime dtime)
• Quote data for the timestamp is in Epoch milliseconds or number of milliseconds after Epoch which for computers is 1970-01-01 00:00. The code LocalDateTime datetime = Instant.ofEpochMilli(toffset).atZone(ZoneId.systemDefault()).toLocalDateTime(); does the conversion.

    public List<Quote> csv_process(String tfile, int startat) throws IOException
    {
        List<Quote> quotes = new ArrayList<Quote>();
        Path pathToFile = Paths.get(tfile);
        try (BufferedReader breader = Files.newBufferedReader(pathToFile, StandardCharsets.UTF_8))
        {
            String line = "";
            int c = 0;
            while (c < startat)
            {
                line = breader.readLine();
                c++;
            }
            while (line != null)
            {
                line = breader.readLine();
                if (line != null) {
                    String G[] = line.split(",");
                    if (G.length >= 8) {
                        try {
                            c++;
                            float open = parseFloat(G[0]);
                            float high = parseFloat(G[1]);
                            float low = parseFloat(G[2]);
                            float close = parseFloat(G[3]);
                            float volw = parseFloat(G[4]);
                            long vol = Integer.parseInt(G[5]);
                            long ntrades = Integer.parseInt(G[6]);
                            long toffset = Long.parseLong(G[7]);
                            LocalDateTime datetime = Instant.ofEpochMilli(toffset).atZone(ZoneId.systemDefault()).toLocalDateTime();
                            Quote newquote = new Quote(open, high, low, close, volw, vol, ntrades, datetime);
                            quotes.add(newquote);
                        } catch (Exception e) {

                        }
                    }
                }
            }
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
        return quotes;
    }
}
class Quote {

    public float open;
    public float high;
    public float low;
    public float close;
    public float  volw;
    public float vol;
    public long ntrades;
    public LocalDateTime dtime;

    public Quote(float open, float high, float low, float close, float volw, float vol, long ntrades, LocalDateTime dtime)
    {
        this.open = open;
        this.high = high;
        this.low = low;
        this.close = close;
        this.volw = volw;
        this.vol = vol;
        this.ntrades = ntrades;
        this.dtime = dtime;
    }
}

Once this is done we return quotes which is of type List<Quote> which is added in lines:

 Quote newquote = new Quote(open, high, low, close, volw, vol, ntrades, datetime);
 quotes.add(newquote);