Remove specific section from text file using java

9:04 PM Posted by Preetish Panda

In this post I'll share a code snippet that will remove specific section from the text file.Suppose your file has following structure:

Something
blah blah blah
START
lines...lines..
more..lines..

END

again some text

Our code will remove all the text present between and including START & END.

Here is the method:

public void removeLineFromFile(String file, String start, String end) {

    try {

      File inFile = new File(file);

      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(file));
      PrintWriter pw = new PrintWriter(new FileWriter(tempFile));

      String line = null;
      Boolean flag=true;
      //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(start)) {
         flag=false;

        }
        if(line.trim().equals(end)){
        flag=true;
        }

        if (flag && !(line.trim().equals(end))){
        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();
    }
}

Happy coding !! :)