Definition

Custom exceptions in Java are user-defined exceptions created by extending the base Exception class (for checked exceptions) or RuntimeException class (for unchecked exceptions). These exceptions help handle specific error scenarios in a more descriptive and application-specific way.

Example

// Define a custom exception
class CustomException extends Exception {
    public CustomException(String message) {
        super(message); // Pass message to the superclass constructor
    }
}

// Example usage
public class CustomExceptionExample {
    // Method that throws the custom exception
    public static void checkNumber(int number) throws CustomException {
        if (number < 0) {
            throw new CustomException("Number cannot be negative: " + number);
        }
        System.out.println("Valid number: " + number);
    }

    public static void main(String[] args) {
        try {
            checkNumber(5);  // Valid case
            checkNumber(-3); // This will throw CustomException
        } catch (CustomException e) {
            System.out.println("Caught Exception: " + e.getMessage());
        }
    }
}

Output

Valid number: 5
Caught Exception: Number cannot be negative: -3

Feature

  • Custom Messages: Allow developers to define detailed error messages specific to the exception.
  • Checked or Unchecked: Developers can choose whether the exception should be checked or unchecked based on the application’s needs.
  • Inheritance: Custom exceptions integrate seamlessly with Java’s exception hierarchy.
  • Centralized Error Handling: Simplifies debugging by categorizing specific types of errors.

Advantages

  • Improved Readability: Provides descriptive and meaningful exception names, helping to understand the problem at a glance.
  • Error-Specific Handling: Facilitates handling specific error scenarios distinct from generic exceptions.
  • Encapsulation: Encapsulates error logic and conditions in one place, making the code modular and easier to maintain.
  • Enhanced Debugging: Helps in debugging by clearly specifying the cause of the exception.
  • Code Reusability: Custom exceptions can be reused across the application, promoting consistency in error handling.

Categorized in:

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