How do I erase everything in my file before adding new stuff?

public void writeToFile(String n) {
 
        //Deklaration
        FileWriter pw = null;
 
        try {
            //Skapa en StringBuffer
            StringBuffer buf = new StringBuffer();
 
            // Lägg till det som ska in i filen.
            buf.append(n).append(" ").append("\r\n");
 
            //Öppna filen
            File outFile = new File("Transaction.txt");
            JOptionPane.showMessageDialog(null, "Filen sparad som Transaction.txt");
            //Finns filen?
            if (!outFile.exists()) {
                outFile.createNewFile();
            }
 
            //Skriv sist i filen
            pw = new FileWriter(outFile, true);
            pw.write(buf.toString());
 
        } catch (Exception e) {
            System.err.print("Gick ej öppna. Avslutar");
            System.exit(-1);
        } //end catch
        finally {
            //Stäng filen
            if (pw != null) {
                try {
                    pw.flush();
                    pw.close();
                } catch (IOException e) {
                    System.err.print("Gick ej stänga filen. Avslutar");
                    System.exit(-1);
                } //end catch
            } //end if
        } //end finnaly
    } //end writeToFile

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