import java.io.IOException;
import org.json.simple.JSONObject;

class JsonDemo {
   public static void main(String[] args) throws IOException {
      JSONObject obj1 = new JSONObject();       
      obj1.put("name", "foo");
      obj1.put("num", new Integer(100)); 

      JSONObject obj2 = new JSONObject();       
      obj2.put("balance", new Double(1000.21));
      obj2.put("is_vip", new Boolean(true));       
      obj1.putAll(obj2);       
      System.out.println(obj1);
   }
}

{"balance":1000.21,"is_vip":true,"num":100,"name":"foo"}