User Defined Exception in Java

Introduction:

Exception handling is an essential aspect of programming, allowing developers to handle and recover from unexpected errors and exceptional scenarios gracefully. Several preset exceptions in Java address typical mistake situations. However, predefined exceptions can fail to capture an application's unique requirements. In certain circumstances, Java enables programmers to define their very own unique exceptions, referred to as User-Defined Exceptions. The significance of User-Defined Exceptions in Java, how to successfully create and utilize them, and their notion are all covered in this article.

Overview:

For Java programs to be stable and reliable, exception handling is essential. It enables programmers to manage faults and extraordinary circumstances without suddenly ending the application. Although Java offers a variety of built-in exceptions, they might not always match an application's particular requirements. User-Defined Exceptions are useful in this situation.

Why use custom exceptions?

Custom exceptions provide several benefits over using only the predefined exceptions. By creating custom exceptions, developers can:

Improve code readability: Custom exceptions can convey specific error conditions that are relevant to the application domain. This improves the expressiveness and readability of the code.

Enhance error reporting: Custom exceptions can contain extra details that are unique to the error, such as error codes, pertinent information, and contextual information. Better error reporting and debugging are the results of this.

Separate business logic from exception handling: Developers may do just that by generating custom exceptions, separating the application's business logic from the code that handles exceptions. The result is cleaner, easier-to-maintain code.

Handle special cases: Using custom exceptions, developers can manage error scenarios unique to a certain application and not covered by the standard exceptions.

What is a User Defined Exception in Java?

A user-defined exception in Java is a special exception the developer makes to deal with particular extraordinary situations in their program. Even while Java comes with a collection of predefined exceptions to deal with typical error situations, there are times when these exceptions may only partially satisfy the needs of a specific application. In these circumstances, developers can design their unique exceptions to handle particular problem scenarios.

User-Defined Exception or one of its subclasses serves as the foundation class from which exceptions are often descended. Developers can design their exception hierarchy by using custom exceptions, where each exception is tailored to a particular error situation or unusual circumstance that is pertinent to the application domain.

The process of creating a User-Defined Exception involves creating a new class that extends the Exception class or extends one of its subclasses, such as RuntimeException. This custom exception class can then be instantiated and thrown within the code to signal an exceptional condition.

How to Create User-Defined Exceptions in Java?

Creating a User-Defined Exception in Java involves a few steps. Let's examine these actions using illustrations, screenshots, and photos.

Specify Exception or one of its subclasses as the base class for your new class: We must declare a new class that extends the base class Exception or one of its subclasses, such as RuntimeException, to produce a unique exception. Here's an illustration:

java
public class CustomException extends Exception { 
    // Constructors, methods, and additional code go here 
}  

Pass the Exception Message to Super Class Constructor and Retrieve It Using the getMessage() Method: The Exception class provides a constructor that accepts a string parameter representing the exception message. By passing the message to the superclass constructor, we can relate an enlightening mistake message with the special case. Here is a model:

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

We may utilize the getMessage() method offered by the Exception class to obtain the exception message. This procedure returns the error message related to the exception. Here's an illustration:

java
try { 
    throw new CustomException("This is a custom exception."); 
} catch (CustomException e) { 
    System.out.println(e.getMessage()); 
}  

Override the toString() Method and Customize It with Our Exception Message: The toString() function of the Exception class transforms the exception object into a string representation. We may modify the By modifying this function, wetput to include the exception message by modifying thisration:

java
public class CustomException extends Exception { 
    public CustomException(String message) { 
        super(message); 
    } 
 
    @Override 
    public String toString() { 
        return "CustomException: " getMessage(); 
    } 
}  

Presently, when we print the special case object, it will show the custom string portrayal that incorporates the exception message.

Examples:

Let's examine some real-world instances of user-defined exceptions in Java, along with pertinent code snippets, pictures, and graphics.

Simple User-Defined Exception in Java: In this example, we show how to throw and catch a straightforward custom exception called CustomException. Here is the key:

java
public class CustomException extends Exception { 
    public CustomException(String message) { 
        super(message); 
    } 
} 
 
public class Main { 
    public static void main(String[] args) { 
        try { 
            throw new CustomException("This is a custom exception."); 
        } catch (CustomException e) { 
            System.out.println(e.getMessage()); 
        } 
    } 
}  

User-Defined Exception for Validating Login Credentials: In this model, we make a special custom case called InvalidCredentialsException to deal with the situation of invalid login qualifications. We exhibit how to utilize this exemption to approve client login qualifications. Here is the code:

java
public class InvalidCredentialsException extends Exception { 
    public InvalidCredentialsException(String message) { 
        super(message); 
    } 
} 
 
public class LoginValidator { 
    public void validateCredentials(String username, String password) throws InvalidCredentialsException { 
        if (!isValid(username, password)) { 
            throw new InvalidCredentialsException("Invalid login credentials."); 
        } 
    } 
 
    private boolean isValid(String username, String password) { 
        // Logic to validate credentials 
    } 
} 
 
public class Main { 
    public static void main(String[] args) { 
        LoginValidator validator = new LoginValidator(); 
        try { 
            validator.validateCredentials("john.doe", "password123"); 
        } catch (InvalidCredentialsException e) { 
            System.out.println(e.getMessage()); 
        } 
    } 
}  

User-Defined Exception for Value Less than Threshold Value: In this model, we make a custom exception called ValueBelowThresholdException to deal with the situation of a worth being under a predetermined limit. We show how to utilize this special case to uphold a base worth necessity. Here is the code:

java
public class ValueBelowThresholdException extends Exception { 
    public ValueBelowThresholdException(String message) { 
        super(message); 
    } 
} 
 
public class ThresholdValidator { 
    public void validateValue(int value, int threshold) throws ValueBelowThresholdException { 
        if (value < threshold) { 
            throw new ValueBelowThresholdException("Value is below the threshold."); 
        } 
    } 
} 
 
public class Main { 
    public static void main(String[] args) { 
        ThresholdValidator validator = new ThresholdValidator(); 
        try { 
            validator.validateValue(5, 10); 
        } catch (ValueBelowThresholdException e) { 
            System.out.println(e.getMessage()); 
        } 
    } 
} 

User-defined Exception for Validity of an Entity

In Java, a User-Defined Exception for the legitimacy of a substance alludes to a custom exception that is made to deal with situations where an element's legitimacy is compromised or doesn't meet specific standards. This sort of special case is commonly used to authorize business rules or limitations on the legitimacy of articles or information inside an application.

Here is a model outlining the utilization of a User-Defined Exception for the legitimacy of an element:

java
public class InvalidEntityException extends Exception { 
    public InvalidEntityException(String message) { 
        super(message); 
    } 
} 
 
public class EntityValidator { 
    public void validateEntity(Entity entity) throws InvalidEntityException { 
        if (!entity.isValid()) { 
            throw new InvalidEntityException("The entity is not valid."); 
        } 
    } 
} 
 
public class Main { 
    public static void main(String[] args) { 
        EntityValidator validator = new EntityValidator(); 
        try { 
            Entity entity = new Entity(); 
            validator.validateEntity(entity); 
        } catch (InvalidEntityException e) { 
            System.out.println(e.getMessage()); 
        } 
    } 
}  

User-defined Exception for Validating the Age of a User: In this model, we make a custom exemption called InvalidAgeException to deal with the situation of an invalid age for a client. We demonstrate how to use this exception to enforce age restrictions. Here's the code:

java
public class InvalidAgeException extends Exception { 
    public InvalidAgeException(String message) { 
        super(message); 
    } 
} 
 
public class UserValidator { 
    public void validateAge(int age) throws InvalidAgeException { 
        if (age < 18 || age > 60) { 
            throw new InvalidAgeException("Invalid age. Age must be between 18 and 60."); 
        } 
    } 
} 
 
public class Main { 
    public static void main(String[] args) { 
        UserValidator validator = new UserValidator(); 
        try { 
            validator.validateAge(16); 
        } catch (InvalidAgeException e) { 
            System.out.println(e.getMessage()); 
        } 
    } 
}  

Conclusion:

Java gives developers the freedom to handle particular fault circumstances that aren't covered by the standard exceptions, thanks to user-defined exceptions. Developers may increase error reporting, write more readable code, and efficiently handle application-specific exceptional circumstances by generating custom exceptions. The idea of user-defined exceptions, their significance, and how to generate and utilize them in Java programs were all covered in this article. We explored different use cases of custom exceptions through various examples, demonstrating their practical implementation.

FAQs:

1. Can I create multiple custom exceptions in a single Java program?

Yes, you can create multiple custom exceptions in a single Java program. Each custom exception can cater to your application's specific error condition or exceptional scenario. Creating multiple custom exceptions allows you to handle different types of errors with precision and clarity.

2. How do I decide whether to create a checked or unchecked custom exception?

The decision to create a checked or unchecked custom exception depends on the nature of the exceptional scenario and the desired error-handling strategy. If the exceptional condition is recoverable and you want to enforce explicit handling, you can create a checked custom exception by extending the Exception class. On the other hand, if the exceptional condition is unlikely to be recovered and you prefer a more flexible error-handling approach, you can create an unchecked custom exception by extending the RuntimeException class.

3. Can I nest custom exceptions within other custom exceptions?

Yes, you can nest custom exceptions within other custom exceptions. This allows you to handle complex exceptional scenarios and provide a hierarchical structure to your custom exceptions.

4. How do I handle custom exceptions along with predefined exceptions?

You can handle custom exceptions along with predefined exceptions by using separate catch blocks for each type of exception. Within each catch block, you can specify the appropriate error-handling logic. You can provide comprehensive error handling and recovery mechanisms in your Java program by catching and handling both custom and predefined exceptions.

5. Can I create custom exception hierarchies?

Indeed, you can make custom exception orders by making subclasses of your custom exceptions. By creating a hierarchy, you can have a base custom exception class and derive more specific exceptions from it, capturing different error conditions with varying levels of detail and specificity.

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