Twilio Programmable Chat API is a powerful tool for adding real-time communication to web applications, and it's easy to use with Java Struts 2 application. To set up Twilio Programmable Chat, you need to create a new chat service and get the service SID and API key. Then, you can add the Twilio library to your project and initialize the chat SDK using the token generated by the `CreateToken` class. The chat SDK provides methods for creating channels, sending messages, and listening for message additions. To display messages, you need to append them to an HTML div with the id "msgItems". The `appendMessage` function is used to add new messages to the interface. Finally, test your finished Struts 2 chat app by loading it in different browser tabs or sharing it with friends and start communicating.