Java WebSocket is a technology that allows for full-duplex communication between a client and a server over a single, long-lived connection. It’s commonly used for building real-time applications where low-latency communication is essential. Here are some key points about Java WebSocket:

1. APIs: Java provides the Java API for WebSocket (JSR 356), which is part of the Java EE 7 specification. This API allows developers to create WebSocket endpoints on the server and WebSocket clients in Java applications.

2. Server-Side: To create a WebSocket server in Java, you typically use a framework like Java EE (Enterprise Edition) or a library like Tyrus. These provide the necessary infrastructure for handling WebSocket connections and messages.

3. Client-Side: On the client side, you can use libraries like Tyrus or Jetty WebSocket to create WebSocket clients in your Java applications. These libraries make it easy to establish WebSocket connections and exchange data with WebSocket servers.

4. Annotations: Java WebSocket APIs often make use of annotations to define WebSocket endpoints and configure them. Annotations like @ServerEndpoint are commonly used to specify the URL at which the WebSocket endpoint should be available.

5. Security: Security considerations are important when working with WebSocket. You need to ensure that your WebSocket connections are secure to protect sensitive data. This can be achieved through protocols like TLS/SSL.

6. Messaging: WebSocket enables bidirectional communication, and messages can be sent in both directions. You can define custom message handling logic in your WebSocket endpoints to process and respond to messages from clients.

7. Use Cases: Java WebSocket is used in various applications, including online gaming, real-time chat applications, financial trading platforms, and any scenario where real-time, low-latency communication is required.