public static void setUser(String username, String password) {
        FileWriter fw;
        try {
            fw = new FileWriter("./web/user.txt", true); //就是这个构造方法的第二个参数，为true则是追加内容

            BufferedWriter bw = new BufferedWriter(fw);
            bw.write(username);
            bw.write(" ");
            bw.write(password);
            bw.write("\n");
            bw.close();
            fw.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        User.setUser("xxxx","xxxxxx");
    }