InputStreamReader

 public static void main(String[] args) throws IOException {
//读取 e:\a.txt 文件到程序
//思路
//1. 创建字符输入流 BufferedReader [处理流]
//2. 使用 BufferedReader 对象读取 a.txt
//3. 默认情况下，读取文件是按照 utf-8 编码,下面的代码是正常的，
// 但是当我们把txt文件改为gbk编码时就会出现乱码
//所以我们可以先用字符流加上指定编码，再转为字符流
// 读取到的内容: {"name":"����","birthday":"2021��12��13�� 02:38:47"}asddff
        String filePath = "a.txt";
        BufferedReader br = new BufferedReader(new FileReader(filePath));
        String s = br.readLine();
        System.out.println("读取到的内容: " + s);
        br.close();
//InputStreamReader
//OutputStreamWriter
    }
}

package com.hspedu.transformation;
import java.io.*;

public class InputStreamReader_ {
public static void main(String[] args) throws IOException {
String filePath = "e:\a.txt";
//解读
//1. 把 FileInputStream 转成 InputStreamReader
//2. 指定编码 gbk
//InputStreamReader isr = new InputStreamReader(new FileInputStream(filePath), "gbk");
//3. 把 InputStreamReader 传入 BufferedReader
//BufferedReader br = new BufferedReader(isr);
//将 2 和 3 合在一起
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(filePath), "gbk"));
//4. 读取
String s = br.readLine();
System.out.println("读取内容=" + s);
//5. 关闭外层流
br.close();
}
}