1. FileOutputStream/FileInputStream 字节流
2. 字符流进阶及BufferedWriter、BufferedReader
InputStreamReader有两个主要的构造函数：
1、InputStreamReader(InputStream in)
2、InputStreamReader(InputStream in, String charsetName)
OutputStreamWriter也有两个主要的构造函数：
1、OutputStreamWriter(OutputStream out)
2、OutputStreamWriter(OutputStream out, String charsetName)
