parse json java result null

Question

I am stucking with parse json in java. Here is my code:

package url.process;

import java.util.ArrayList;
import java.util.List;
import org.json.simple.JSONArray;
import org.json.simple.JSONAware;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;

public class jsonArray implements JSONAware{

private long l;

public jsonArray(long l){
    this.l=l;
}

public long getArray(){
    return l;
}
public void setArray(long l){this.l=l;}

@Override
public String toJSONString() {
    StringBuilder sb = new StringBuilder();
    sb.append("{");
    sb.append("\""+getArray()+"\"");
    sb.append("}");
    return sb.toString();
}

public static void main(String[] args){
   // doc doi tuong thanh chuoi
    List <jsonArray> listjsonarray = new ArrayList<jsonArray>(){  
        {
            add( new jsonArray(76543456));
            add( new jsonArray(112233445));
            add( new jsonArray(546372));
            add( new jsonArray(9876553));
        }
    };
    System.out.println(JSONArray.toJSONString(listjsonarray));

    //doc chuoi thanh doi tuong
    String jsonString = "[{\"76543456\"},"+"{\"112233445\"},"+"{\"546372\"},"+"{\"9876553\"}]";
    try{
        JSONParser jsonParser = new JSONParser();
        JSONArray jsonArray = (JSONArray) jsonParser.parse(jsonString);

        for(int i =0;i<jsonArray.size();i++){
            JSONObject jsonObject = (JSONObject) jsonArray.get(i);
            long l = Long.parseLong((String) jsonObject.get("l"));
            jsonArray ja = new jsonArray(l);
            System.out.println("Elements is "+ja.getArray());
        }
    }catch(Exception e){
        System.out.println(e.getMessage());
    }
}

}

The result is : [{"76543456"},{"112233445"},{"546372"},{"9876553"}] null

I do not know to parse this array above. Please help me, thank you so much and have a good time.

Answer 1

Your JSON is invalid. Braces {} indicate a JSON object which contains key-value pairs. But you are putting JSON strings in them.

[{"76543456"},{"112233445"},{"546372"},{"9876553"}]

Perhaps you meant to have

["76543456","112233445","546372","9876553"]

The JSON format is described here .

You'll have other problems later when trying to cast a String to a JSONObject . Handle those appropriately. If you're storing JSON strings, you should get back Java String objects.

Answer 2

JSON is a key value data structure. For example, a JSON object is as follow:

{"name" : "John Smith"}

The string you input there doesn't follow the convention of JSON, therefore the program couldn't work

Answer 3

The null output is because of

}catch(Exception e){
    System.out.println(e.getMessage());
});

The json is not valid and therefore you get a ParseException and this exception has no message.

As I can see you want to get the l property of the JSONObject

long l = Long.parseLong((String) jsonObject.get("l"));

in this case the correct json would be

String jsonString = "[{\"l\": \"76543456\"},"+"{\"l\": \"112233445\"},"+"{\"l\": \"546372\"},"+"{\"l\": \"9876553\"}]";