java通过编码读取文件

 String s = "我爱你中国";
        OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("ac1.txt"), "gbk");
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("ac.txt"), "gbk"));
        bufferedWriter.write(s);
        osw.write(s);
        osw.close();
        bufferedWriter.close();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream("ac1.txt"), "gbk"));
        String len;
        while ((len = bufferedReader.readLine()) != null) {
            System.out.println(len);
        }
        bufferedReader.close();