UML Diagram Expert

How do I create a simple state in a state diagram?

Create a class diagram for a library system ?

Can you help me integrate JSON data into my state diagram?

Integrating real-world data into diagrams can enhance their practicality. How can I seamlessly incorporate JSON data into my state diagrams to reflect dynamic system behaviors?

I've read about forks and joins being used to manage parallel processes in state diagrams. Could you demonstrate their application with an example that illustrates managing concurrent activities within a system?

I'm new to UML diagrams. Can you guide me through creating my first state in a state diagram, emphasizing the details I need to include for it to be effective?