What is the basis of the exception hierarchy structure and why is it built this way?

The hierarchy of exceptions in Java is based on the Throwable class, from which two main subclasses inherit: Error and Exception.

• Error represents serious errors that are usually not handled by the application (e.g., OutOfMemoryError).
• Exception are exceptions that can be handled by the program.

Further, Exception is divided into:

• Checked exceptions — require mandatory handling or declaration in the method (e.g., IOException).
• Unchecked exceptions, descendants of RuntimeException — do not require mandatory handling (e.g., NullPointerException).

This structure allows:

• Clearly separating errors that can and should be handled from errors that are usually critical.
• Ensuring strict typing and control over exception handling at compile time.
• Improving code readability and maintainability, as the developer can see what exceptions may occur and how to work with them.