# Reference App
source: https://developer.mastercard.com/straight-through-processing/documentation/reference-app/index.md

## Overview {#overview}

We have provided a simple reference application in Java that you can download to get started quickly. The application uses a pre-generated Open API client using the STP Swagger file. Once downloaded, navigate to the `Main.java` file (in the `src/main/java/org/openapitools/client` directory) and follow the instructions in the comments.

Please note that the reference application works with the Sandbox environment, which does not process a payment. The responses from the Sandbox environment are simulated responses. Please work with your Mastercard representative to receive the Supplier details required for registration within the STP APIs.

## Get the source code {#get-the-source-code}

The source code for this tutorial can be found [here](https://static.developer.mastercard.com/content/straight-through-processing/swagger/client_stp.zip).