转换流：把字节流转换为一个字符流

可以有效避免乱码的问题

例子

import java.io.*;
public class Main {
    public static void main(String[] args) throws Exception {
        String path = "./story.txt";
        boolean append = false;
        // 指定编码 GBK
        InputStreamReader isr = new InputStreamReader(new FileInputStream(path), "gbk");
        BufferedReader br = new BufferedReader(isr);
        String line = br.readLine();
        br.close();
        System.out.println("读取到的内容：" + line);
    }
}