try {
        BufferedReader reader = new BufferedReader(new FileReader(file));
        BufferedWriter writer = new BufferedWriter(new FileWriter(toFile));
        String line = null;
        while ((line = reader.readLine()) != null) {
            writer.write(line);
            writer.newLine();
            writer.flush();
        }
        reader.close();
        writer.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

• 在while当中需要用一个变量缓存读到的文本，否则会有缺失文本的情况，也就是read方法读一次就不会再读第二次