FileOutputStream fileOutputStream = null;
OutputStreamWriter outputStreamWriter = null;
BufferedWriter bufferedWriter = null;
File file = new File("D:/test.txt");
fileOutputStream = new FileOutputStream(file, true);
outputStreamWriter = new OutputStreamWriter(fileOutputStream);
bufferedWriter = new BufferedWriter(outputStreamWriter);
for (String conent : allFilePath) {
bufferedWriter.write("," + conent);
}