Best How To :

I wrote a quick method for you that I think does what you want, i.e. remove all occurrences of a token in a line, where that token is embedded in the line and is identified by a leading dash.

The method reads the file and writes it straight out to a file after editing for the token. This would allow you to process a huge file without worrying about about memory constraints.

You can simply rename the output file after a successful edit. I'll leave it up to you to work that out.

If you feel you really must use string buffers to do in memory management, then grab the logic for the line editing from my method and modify it to work with string buffers.

static void onePassReadEditWrite(final String inputFilePath, final String outputPath)
{
    // the input file
    Scanner inputScanner = null;
    // output file
    FileWriter outputWriter = null;

    try
    {
        // open the input file
        inputScanner = new Scanner(new File(inputFilePath));
        // open output file
        File outputFile = new File(outputPath);
        outputFile.createNewFile();
        outputWriter = new FileWriter(outputFile);

        try
        {

            for (
                    String lineToEdit = inputScanner.nextLine();
                    /*
                     * NOTE: when this loop attempts to read beyond EOF it will throw the
                     * java.util.NoSuchElementException exception which is caught in the
                     * containing try/catch block.
                     * 
                     *  As such there is NO predicate required for this loop.
                    */;
                    lineToEdit = inputScanner.nextLine()
                )
                // scan all lines from input file
            {
                System.out.println("START LINE [" + lineToEdit + "]");

                // get position of dash in line
                int dashInLinePosition = lineToEdit.indexOf('-');

                while (dashInLinePosition != -1)
                    // this line has needs editing
                {

                    // split line on dash
                    String halfLeft = lineToEdit.substring(0, dashInLinePosition);
                    String halfRight = lineToEdit.substring(dashInLinePosition + 1);
                    // get token after dash that is to be removed from whole line
                    String tokenToRemove = halfRight.substring(0, 2);
                    // reconstruct line from the 2 halves without the dash
                    StringBuilder sb = new StringBuilder(halfLeft);
                    sb.append(halfRight.substring(0));

                    lineToEdit = sb.toString();

                    // get position of first token in line
                    int tokenInLinePosition = lineToEdit.indexOf(tokenToRemove);

                    while (tokenInLinePosition != -1)
                        // do for all tokens in line
                    {
                        // split line around token to be removed
                        String partLeft = lineToEdit.substring(0, tokenInLinePosition);
                        String partRight = lineToEdit.substring(tokenInLinePosition + tokenToRemove.length());

                        if ((!partRight.isEmpty()) && (partRight.charAt(0) == ','))
                            // remove prefix comma from right part
                        {
                            partRight = partRight.substring(1);
                        }

                        // reconstruct line from the left and right parts
                        sb.setLength(0);
                        sb = new StringBuilder(partLeft);
                        sb.append(partRight);
                        lineToEdit = sb.toString();

                        // find next token to be removed from line
                        tokenInLinePosition = lineToEdit.indexOf(tokenToRemove);
                    }

                    // handle additional dashes in line
                    dashInLinePosition = lineToEdit.indexOf('-');
                }

                System.out.println("FINAL LINE [" + lineToEdit + "]");

                // write line to output file
                outputWriter.write(lineToEdit);
                outputWriter.write("\r\n");
            }

        }
        catch (java.util.NoSuchElementException e)
            // end of scan
        {
        }
        finally
            // housekeeping
        {
            outputWriter.close();
            inputScanner.close();
        }

    }
    catch(FileNotFoundException e)
    {
        e.printStackTrace();
    }
    catch(IOException e)
    {
        inputScanner.close();

        e.printStackTrace();
    }

}