Problem with JSON in java

public void Datos(String id){
        long idLg = Long.parseLong(id);
        long flagLg = 8389633;
        JsonObject recibejson = new JsonObject();
        recibejson.addProperty("id", idLg);
        recibejson.addProperty("flags", flagLg);
        //recibejson = recibejson+"&sid=026cc36f88a8c46099a3ff3e48eace36";
        //System.out.println("JSON: " + recibejson + "&sid="+);
        //return recibejson.toString();
        RemoteHttpClient remoteHttpClient = RemoteHttpClient.getInstance();
        remoteHttpClient.remoteCall("core/search_item", recibejson, new ResponseHandler(){
            //url="core/search_item"+
            //remoteHttpClient.remoteCall(url, new ResponseHandler(){
            @Override
            public void onSuccess(String response)
            {
                System.out.println("Esto es lo que recibe");
            }
            @Override
            public void onFailure(int errorCode, Throwable throwableError) {
                super.onFailure(errorCode, throwableError);
                // search item failed, print error
                System.out.println(Errors.getErrorText(errorCode));
            }

        });