Modifying existing file content in Java

Question

I want to replace the second line file content, can somebody help please based on the below file format and listener method.

1324254875443 1313131 Paid 0.0 

2nd line is long and want to replace to currentTimeMillis().

/************** Pay Button Listener **************/ public class payListener implements ActionListener {     public void actionPerformed(ActionEvent e) {          ArrayList<String> lines = new ArrayList<String>();         String line = null;          try {             FileReader fr = new FileReader("Ticket/" + ticketIDNumber + ".dat");             BufferedReader br = new BufferedReader(fr);             FileWriter fw = new FileWriter("Ticket/" + ticketIDNumber + ".dat");             BufferedWriter bw = new BufferedWriter(fw);             while ((line = br.readLine()) != null) {                 if (line.contains("1313131"))                     line.replace(System.currentTimeMillis();                 lines.add(line);                 bw.write(line);             }  //end if                           }     //end try         catch (Exception e) {          }  //end catch        }    //end while }//end method 

Answer 1

As proposed in the accepted answer to a similar question:

open a temporary file in writing mode at the same time, and for each line, read it, modify if necessary, then write into the temporary file. At the end, delete the original and rename the temporary file.

Based on your implementation, something similar to:

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException;  public class ReplaceFileContents {    public static void main(String[] args) {      new ReplaceFileContents().replace();    }     public void replace() {       String oldFileName = "try.dat";       String tmpFileName = "tmp_try.dat";        BufferedReader br = null;       BufferedWriter bw = null;       try {          br = new BufferedReader(new FileReader(oldFileName));          bw = new BufferedWriter(new FileWriter(tmpFileName));          String line;          while ((line = br.readLine()) != null) {             if (line.contains("1313131"))                line = line.replace("1313131", ""+System.currentTimeMillis());             bw.write(line+"\n");          }       } catch (Exception e) {          return;       } finally {          try {             if(br != null)                br.close();          } catch (IOException e) {             //          }          try {             if(bw != null)                bw.close();          } catch (IOException e) {             //          }       }       // Once everything is complete, delete old file..       File oldFile = new File(oldFileName);       oldFile.delete();        // And rename tmp file's name to old file name       File newFile = new File(tmpFileName);       newFile.renameTo(oldFile);     } }