Java IO

按指定格式读取/写入文件

关键：InputStreamReader(InputStream in, String charsetName)，OutputStreamWriter(OutputStream out, String charsetName)

通过InputStreamReader，OutputStreamWriter，我们可以指定输入/输出流的格式，从而进行文件的格式转换

/**
     * 指定格式读取GBK文件/写入UTF-8文件
     */
private static void characterIOCharsetTest() {
    String s = "./resources/dir1/dir11/123.txt";
    File f = new File(s);
    File f2 = new File("./resources/dir1/dir11/123-CharsetCopy.txt");
    StringBuilder sb = new StringBuilder();

    //f是GBK格式文件，所以以GBK格式的InputStreamReader读取，再被BufferedReader包装一层
    try (BufferedReader gbkReader = new BufferedReader(new InputStreamReader(new FileInputStream(f), "GBK"));) {
        String line;
        while ((line = gbkReader.readLine()) != null) {
            sb.append(line);
            //因为line不包含最后的换行符，所以要手动加上去
            sb.append("
");
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    //f2是目的文件，以UTF-8格式存储，所以以UTF-8格式的OutputStreamWriter写入，被BufferedWriter包装一层
    try (BufferedWriter utf8Writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(f2), "UTF-8"))) {
        utf8Writer.write(sb.toString());
    } catch (IOException e) {
        e.printStackTrace();
    }

}

整合版本

/**
     * 整合版
     * 相当于将GBK格式的文件转换到UTF8格式的文件
     */
private static void characterIOCharsetTest2() {
    String s = "./resources/dir1/dir11/123.txt";
    File f = new File(s);
    File f2 = new File("./resources/dir1/dir11/123-CharsetCopy.txt");
    //f是GBK格式文件，所以以GBK格式的InputStreamReader读取，再被BufferedReader包装一层
    //f2是目的文件，以UTF-8格式存储，所以以UTF-8格式的OutputStreamWriter写入，被BufferedWriter包装一层
    try (BufferedReader gbkReader = new BufferedReader(new InputStreamReader(new FileInputStream(f), "GBK"));
         BufferedWriter utf8Writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(f2), "UTF-8"))) {
        String line;
        while ((line = gbkReader.readLine()) != null) {
            //因为line不包含最后的换行符，所以要手动加上去
            utf8Writer.write(line + "
");
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}