How do you differentiate between system and user exceptions? What is the difference in their usage?

System exceptions are errors that occur due to problems within the system itself, such as database errors, memory shortages, or network errors. They are usually generated by the runtime environment or external components and often indicate unexpected failures.

Custom exceptions are created by developers to handle business logic or specific application conditions, such as "User not found" or "Insufficient permissions."

Differences in usage:

• System exceptions are typically not handled at the business logic level but are logged or lead to a crash.
• Custom exceptions allow controlling the flow of execution, providing understandable messages, and responding appropriately to expected errors.

Example in Java:

// Custom exception
class UserNotFoundException extends Exception {
    public UserNotFoundException(String message) {
        super(message);
    }
}

// Usage
if (user == null) {
    throw new UserNotFoundException("User with this ID not found");
}