Custom Exceptions

Custom exceptions allow you to create your own exception classes to handle specific errors in your program. This tutorial will teach you how to define and use custom exceptions.

Creating a Custom Exception

To create a custom exception, extend the Exception class:

class CustomException extends Exception {
    public CustomException(String message) {
        super(message);
    }
}
      

Throwing a Custom Exception

You can throw a custom exception using the throw keyword:

public class Main {
    public static void main(String[] args) {
        try {
            validate(10);
        } catch (CustomException e) {
            System.out.println("Caught the exception");
            System.out.println(e.getMessage());
        }
    }
    
    static void validate(int number) throws CustomException {
        if (number < 20) {
            throw new CustomException("Number is less than 20");
        }
    }
}
      

In this example, the validate method throws a CustomException if the number is less than 20.

Handling a Custom Exception

Handle a custom exception using a try-catch block:

public class Main {
    public static void main(String[] args) {
        try {
            validate(15);
        } catch (CustomException e) {
            System.out.println("Caught the custom exception");
            System.out.println(e.getMessage());
        }
    }
    
    static void validate(int number) throws CustomException {
        if (number < 18) {
            throw new CustomException("Age must be at least 18");
        } else {
            System.out.println("Valid age");
        }
    }
}
      

In this example, the validate method throws a CustomException if the age is less than 18.

Continue exploring our intermediate tutorials to learn more about Java programming.