ArrayList<HashMap<String,String>> to JSON object Java

Question

I want to create a String as follows.

[{ "Name":"David",
 "Age":"30"
 },
 {"Name":"Max",
 "Age":"20"
 }
]

How can we create this string using ArrayList<HashMap<String,String>> and JSON in Java?

• Kartic: This link will help you: stackoverflow.com/questions/12155800/…
• creative Pro: json.org/javadoc/org/json/JSONObject.html is not working. Could you please explain a little bit? I am new to java. I have ArrayList<HashMap<String,String>> with all data. I just want to prepare a JSON string from that as above. Also note that there is no JSON key
• sanky jain: @creative Pro did you tried my solution

Answer 1

Try as below

public String listmap_to_json_string(List<HashMap<String, String>> list)
{ 
 JSONArray json_arr=new JSONArray();
 for (Map<String, String> map : list) {
 JSONObject json_obj=new JSONObject();
 for (Map.Entry<String, String> entry : map.entrySet()) {
 String key = entry.getKey();
 String value = entry.getValue();
 try {
 json_obj.put(key,value);
 } catch (JSONException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 } 
 }
 json_arr.put(json_obj);
 }
 return json_arr.toString();
}

Answer 2

My JSON library fits your use case exactly. For example:

ArrayList<HashMap<String,String>> outer = new ArrayList<HashMap<String,String>>();
HashMap<String,String> inner = new HashMap<String,String>();
inner.put("Name", "David");
inner.put("Age", "30");
outer.add(inner);
inner = new HashMap<String,String>();
inner.put("Name", "Max");
inner.put("Age", "20");
outer.add(inner);
//----------
import io.nayuki.json.Json;
String jsonText = Json.serialize(outer);
System.out.println(jsonText);

Output text:

[{"Age": "30", "Name": "David"}, {"Age": "20", "Name": "Max"}]

Answer 3

Try Jackson Mapper You can read some tutorials about it. You can write code, using Jackson in this manner:

ObjectMapper mapper = new ObjectMapper();
jsonString = mapper.writeValueAsString(listOfMap);