Json-simple
JSON.simple is a simple Java toolkit for JSON. You can use JSON.simple to encode or decode JSON text.
Example
Encode a JSON object
//import org.json.simple.JSONObject;
JSONObject obj=new JSONObject();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);
System.out.print(obj);