Appending data to a text file in Android

I am trying to add data to a text file in android using the code below but it only overwrites the data with one line of data.

private void copyImageToMemory(File outFile , Float number) { try {

    BufferedOutputStream fos = new BufferedOutputStream(
            new FileOutputStream(outFile));


    PrintWriter pw = new PrintWriter(new BufferedWriter(
            new OutputStreamWriter(fos)));

    pw.append("result"+number);
    pw.close();
    maxSpeed=0;

} catch (FileNotFoundException e) {
    Log.e(TAGFile, "FileNotFoundException");
}

}