json格式文件读取，坐标系转换，替换

java 如何读取js格式文件，并将文本中坐标系进行转换替换？
文件格式如下：
var dayData = [[{"COLUMN4_MAX":7640,"COLUMN2":"119.828916,30.298656"},{"COLUMN4_MAX":7577,"COLUMN2":"120.049416,30.235656"}],[{"COLUMN4_MAX":7640,"COLUMN2":"119.828916,30.298656"},{"COLUMN4_MAX":7577,"COLUMN2":"120.049416,30.235656"}]]

package com.mzw;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;

import org.json.JSONArray;
import org.json.JSONObject;

public class TestC {

    public static void main(String[] args) {
        //读取文件内容
        String str = readTxt("C:/Users/Administrator/Desktop/qwe.js");
        //截取字符串
        str = str.substring(str.indexOf("=")+1,str.length()).trim();
        //判断是否为数组
        if(str.startsWith("[")){
            JSONArray jsonArray = new JSONArray(str);

            for (Object obj : jsonArray) {

                for (Object obj2 : ((JSONArray)obj)) {
                    String COLUMN2 = ((JSONObject)obj2).get("COLUMN2").toString();
                    String COLUMN4_MAX = ((JSONObject)obj2).get("COLUMN4_MAX").toString();
                    //打印数据
                    System.out.println("COLUMN2 : " + COLUMN2 + " , COLUMN4_MAX : " + COLUMN4_MAX);
                }
            }
        }
    }

    // 读取文件数据
    public static String readTxt(String txtPath) {
        File file = new File(txtPath);
        if(file.isFile() && file.exists()){
            try {
                FileInputStream fileInputStream = new FileInputStream(file);
                InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream,"UTF-8");
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

                StringBuffer sb = new StringBuffer();
                String text = null;
                while((text = bufferedReader.readLine()) != null){
                    if(!"".equals(text) && text != null){
                        if(text.length() > 3){
                            sb.append(text.replaceAll(" ", ","));
                            sb.append(",");
                        }
                    }
                }
                return sb.toString();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return null;
    }
}