Lecture 91:-  User Defined Exeptions

In Java, you can create your own custom exceptions, known as user-defined exceptions, by extending the existing exception classes. User-defined exceptions allow you to handle specific error conditions in your application and provide meaningful and customized error messages to users.

To create a user-defined exception, follow these steps:

1. Create a new class that extends an existing exception class (usually Exception or one of its subclasses like RuntimeException).
2. Define a constructor for your custom exception class. You can use this constructor to set a custom error message or perform other initialization tasks.
3. Optionally, you can add any additional methods or fields to your custom exception class to provide more information or behavior specific to your application.

Here's an example of creating a user-defined exception:

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// User-defined exception class class InvalidAgeException extends Exception {    public InvalidAgeException(String message) {        super(message);    } } // Application class public class CustomExceptionExample {    public static void main(String[] args) {        try {            int age = -5;            if (age < 0) {                throw new InvalidAgeException("Age cannot be negative.");            }            System.out.println("Age: " + age);        } catch (InvalidAgeException e) {            System.out.println("Error: " + e.getMessage());        }    } }

In this example, we create a custom exception called InvalidAgeException by extending the Exception class. The constructor of the custom exception takes a message as an argument and passes it to the superclass constructor using the super keyword.

In the main method, we throw the InvalidAgeException if the age is negative. When the exception is thrown, the control is transferred to the catch block that matches the InvalidAgeException, and the error message "Error: Age cannot be negative." is displayed.

User-defined exceptions allow you to tailor exception handling to the specific requirements of your application. By creating custom exception classes, you can provide better error reporting, more informative error messages, and specific exception handling logic that suits the needs of your application domain.