java 通过字符流读取json文件、修改json文件

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;



public class OperateFile {

    /**
     * 从文件中读取信息，并转换为相应对象
     * @return
     */
    public static FileDto readFileDto(){
        File file = new File("c://test.json");
        if(!file.exists()){
            return null;
        }
        FileDto dto = null;
        BufferedReader br = null;
        try {
            br = new BufferedReader(new InputStreamReader(new FileInputStream(file),"UTF-8"));
            StringBuilder sb = new StringBuilder();
            String line;
            while((line = br.readLine()) != null){
                sb.append(line);
            }
            dto = JSONObject.parseObject(sb.toString(),FileDto.class);
            br.close();
        } catch (UnsupportedEncodingException | FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return dto;
    }

    /**
     * 将对象写入缓存文件中
     * @author 
     */
    public static void writeFileDto(FileDto dto){
        File file = new File("c://test.json");
        if(!file.exists()){
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        try {
            String jsonStr = JSON.toJSONString(dto);
            BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file),"UTF-8"));
            bw.write(jsonStr);
            bw.flush();
            bw.close();
        } catch (UnsupportedEncodingException | FileNotFoundException e) {
            e.printStackTrace();
        }catch (IOException e) {
            e.printStackTrace();
        }
    }
}