Modifying complex csv files in java

Question

I wanted to write a program which can print, and modify the irregular csv files. The format is as follows:

    1.date
    2.organization name
    3. student name         


        

Answer 1

I think this should be helpful for you. Basically there should be some pattern in your messed up csv. Below is my code to arrange your csv

   public static void main(String[] args) throws FileNotFoundException, UnsupportedEncodingException {

        PrintWriter writer = new PrintWriter("file.txt", "UTF-8");
            try{

              //Create object of FileReader
              FileReader inputFile = new FileReader("csv.txt");

              //Instantiate the BufferedReader Class
              BufferedReader bufferReader = new BufferedReader(inputFile);

              //Variable to hold the one line data
              String line;
              String date="";String org ="";String student ="";
              // Read file line by line and print on the console
              while ((line = bufferReader.readLine()) != null)   {
                  if(line.contains("1.")){
                      if(date!="" || org!=""){
                          writer.println(date+","+org+","+student);
                          student ="";
                       }
                         date = line.substring(2);
                        }else if(line.contains("2.")){
                            org = line.substring(2);

                      }else{
                            line = "("+line+")";
                          student += line+",";
                  }

                    System.out.println(line);
              }
              writer.println(date+","+org+","+student);
              //Close the buffer reader
              bufferReader.close();
      }catch(Exception e){
        System.out.println("Error while reading file line by line:" + e.getMessage());                      
   }
       writer.close();
  }

This is the output you will get for this

   10/09/2016, cycling club,(3. sam, 1000, oklahoma),(   henry, 1001, california),(   bill, 1002, NY),
   11/15/2016, swimming club,(3. jane, 9001, georgia),(   elizabeth, 9002, lousiana),

I am reading the file from csv.txt. while loop goes through each line of text file.all the fields are stored in a variable. When next date comes I write all of them into output file. Last line of the csv is written to file after the while loop terminates.

Answer 2

Try uniVocity-parsers to handle this. For parsing this sort of format, you'll find a few examples here. For writing, look here and here.

Adapting from the examples I've given, you could write:

final ObjectRowListProcessor dateProcessor = new ObjectRowListProcessor();
final ObjectRowListProcessor clubProcessor = new ObjectRowListProcessor();
final ObjectRowListProcessor memberProcessor = new ObjectRowListProcessor();

InputValueSwitch switch = new InputValueSwitch(0){
    public void rowProcessorSwitched(RowProcessor from, RowProcessor to) {
    //your custom logic here
    if (to == dateProcessor) {
        //processing dates.
    }
    if (to == clubProcessor) {
        //processing clubs.
    }
    if (to == memberProcessor){
        //processing members
    }
};

switch.addSwitchForValue("1.", dateProcessor, 1);  //getting values of column 1 and sending them to `dateProcessor`
switch.addSwitchForValue("2.", clubProcessor, 1); //getting values of column 1 and sending them to `clubProcessor`
switch.addSwitchForValue("3.", memberProcessor, 1, 2, 3); //getting values of columns 1, 2, and 3 and sending them to `memberProcessor` 
setDefaultSwitch(memberProcessor, 1, 2, 3); //Rows with blank value at column 0 are members. Also get columns 1, 2, and 3 and send them to `memberProcessor`

CsvParserSettings settings = new CsvParserSettings(); //many options here, check the tutorial and examples

// configure the parser to use the switch
settings.setRowProcessor(switch);

//creates a parser
CsvParser parser = new CsvParser(settings);

//parse everying. Rows will be sent to the RowProcessor of each switch, depending on the value at column 0.
parser.parse(new File("/path/to/file.csv")); 

Disclaimer: I'm the author of this library, it's open-source and free (Apache 2.0 license)