使用for循环将java arraylist转换为数组 [英] convert java arraylist to array using for loop

问题描述

我在这里查看了许多类似的主题，没有一个让我解决:

I have viewed the many similar topics here, none have allowed me to resolve:

 //how to Convert this arraylist to array string using loop

public static void main(String[] args) 
{   
Main m = new Main();
List<JSONObject> jObj = m.getJsonObject();
for (int i = 0; i < jObj.size(); i++) 
    {
    System.out.println(jObj.get(i));
    }
 }  

我看到的许多示例都通过添加代码来创建数组列表，我已经有了arrayList.我只需要将其修改为数组字符串而不是arrayList，以便可以使用

The many examples I have seen all create an array list by adding in the code, I already have the arrayList. I just need to modify it as an array string and not an arrayList so that I may properly format it as a JSON string with

String responseStr = "{\"data\":" + 

这是整个豆子:

package com.queryData.main;

import com.queryData.dao.DataDAO;
import com.queryData.services.JsonServices;
import java.sql.ResultSet;
import java.util.List;
import org.json.JSONObject;

public class Main {
    ResultSet resultSet = null;
    DataDAO datadao = new DataDAO();

    public List<JSONObject> getJsonObject()
    {
        resultSet = datadao.getResultSet();
        List<JSONObject> resList = JsonServices.getFormattedResult(resultSet);      
        return resList;
    }
    //how to Convert this arraylist to array string using loop

    public static void main(String[] args) 
    {   
    Main m = new Main();
    List<JSONObject> jObj = m.getJsonObject();
    for (int i = 0; i < jObj.size(); i++) 
        {
        System.out.println(jObj.get(i));
        }
     }
}

我尝试了以下代码，但是它不起作用.

I tried the following code, but it does not work.

package com.queryData.main;

import com.queryData.dao.DataDAO;
import com.queryData.services.JsonServices;
import java.sql.ResultSet;
import java.util.List;
import org.json.JSONObject;

public class Main {
    ResultSet resultSet = null;
    DataDAO datadao = new DataDAO();

    public List<JSONObject> getJsonObject()
    {
        resultSet = datadao.getResultSet();
        List<JSONObject> resList = JsonServices.getFormattedResult(resultSet);      
        return resList;
    }
    //how to Convert this arraylist to array string using loop

    public static void main(String[] args) 
    {   
    Main m = new Main();
    List<JSONObject> jObj = m.getJsonObject();
    for (int i = 0; i < jObj.size(); i++) 
        {
        //System.out.println(jObj.get(i));
        }

    String[] stringArr = jObj.toArray( new String[] {} );
    for ( String element : stringArr ) {
        System.out.println( element );


     }
    }   
}

任何建议，我们将不胜感激. 谢谢

Any suggestions greatly appreciated. Thanks

推荐答案

使用StringBuilder构建String:

Use StringBuilder to build String :

List<Object> jObj = m.getJsonObject();
StringBuilder sb = new StringBuilder();
for(int i =0 ; i < jObj.size(); i++){
   sb.append(jObj.get(i).toString());
}

最后sb.toString()将是您想要的字符串.

Finally sb.toString() will be your desired String.

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