How to Delete Line in PrintWriter

Question

I am writing a program in Java that writes several lines of information into a CSV file. I want to delete the last line of CSV file, as it is not needed. How would I do this, as the CSV file is created by a PrintWriter, and I don't believe the append method could do this.

The extra line is written because the loop continues for one extra line. This portion of the code is as follows:

public static void obtainInformation() throws IOException {

    PrintWriter docketFile = new PrintWriter(new FileWriter("ForclosureCourtDockets"+startingMonth+"_"+startingDay+"_"+startingYear+"-"+endingMonth+"_"+endingDay+"_"+endingYear+".csv", true)); 
    pageContentString = pageContentString.replace('"','*');
    int i = 0;
    boolean nextDocket = true;

    while(nextDocket) {
      nextDocket = false;

      String propertyCity = "PropertyCity_"+i+"*>"; 
      Pattern propertyCityPattern = Pattern.compile("(?<="+Pattern.quote(propertyCity)+").*?(?=</span>)");
      Matcher propertyCityMatcher = propertyCityPattern.matcher(pageContentString); 

      while (propertyCityMatcher.find()) {
        docketFile.write(i+propertyCityMatcher.group().toString()+", "); 
        nextDocket = true;
      }

      String descriptionValue = "Description_"+i+"*>"; 
      Pattern descriptionPattern = Pattern.compile("(?<="+Pattern.quote(descriptionValue)+").*?(?=</span>)");
      Matcher descriptionMatcher = descriptionPattern.matcher(pageContentString); 

      while (descriptionMatcher.find()) {
        docketFile.write(descriptionMatcher.group().toString()+"\n"); 
      }

      i++;
    }

    docketFile.close();

  }

 public static void removeLineFromFile() {

try {

  File inFile = new File("ForclosureCourtDockets"+startingMonth+"_"+startingDay+"_"+startingYear+"-"+endingMonth+"_"+endingDay+"_"+endingYear+".csv");

  if (!inFile.isFile()) {
    System.out.println("Parameter is not an existing file");
    return;
  }

  //Construct the new file that will later be renamed to the original filename.
  File tempFile = new File(inFile.getAbsolutePath() + ".tmp");

  BufferedReader br = new BufferedReader(new FileReader("ForclosureCourtDockets"+startingMonth+"_"+startingDay+"_"+startingYear+"-"+endingMonth+"_"+endingDay+"_"+endingYear+".csv"));
  PrintWriter pw = new PrintWriter(new FileWriter(tempFile));

  String line = null;

  //Read from the original file and write to the new
  //unless content matches data to be removed.
  while ((line = br.readLine()) != null) {

    if (!line.trim().equals("^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^")) {

      pw.println(line);
      pw.flush();
    }
  }
  pw.close();
  br.close();

  //Delete the original file
  if (!inFile.delete()) {
    System.out.println("Could not delete file");
    return;
  }

  //Rename the new file to the filename the original file had.
  if (!tempFile.renameTo(inFile))
    System.out.println("Could not rename file");

}
catch (FileNotFoundException ex) {
  ex.printStackTrace();
}
catch (IOException ex) {
  ex.printStackTrace();
}
 }

Answer 1

Well, as PrintWriter is just a Writer, which can only append/write/print
So, you can't override the line which you just have written.
Several options you have :

• Modify your logic to make sure you don't write the line you want to remove eventually (I think the most logical option)
• After writing to file you can use another Reader(say, BufferedReader) to read it again, and then re-write it, without the line you'd like to exclude.
• use RandomAccessFile and its seek method to go back and rewrite / remove the line you need.