Contenido del Curso

Java JUnit Library. Types of Testing

1. Testing in Development

What is Testing, and Why do We Need It Types of Testing Application Stages Unit Testing Integration Testing Functional Testing Section 1 Summary

2. Unit Tests

Set-Up Test-Driven Development Creating Unit Tests @BeforeEach How to Test `void` Methods Assertions Assertions Practice Section 2 Summary

3. Exceptions

Throwing Exceptions Try-catch structure Handling Multiple Exceptions Handling Exceptions Practice Creating Exceptions Testing Exceptions Testing Exceptions Practice

Java JUnit Library. Types of Testing

Creating Exceptions

It's time to move on to creating your own custom exceptions that you can throw in your programs. First, it's important to note that there are two types of exceptions.

Types of Exceptions in Java

Checked Exceptions: These are exceptions that must be either caught or declared in the method signature. They are checked at compile-time.
Example: IOException;
Unchecked Exceptions: These exceptions are not checked at compile time. They usually indicate programming errors, such as logic mistakes or incorrect API usage.
Example: NullPointerException.

Note
You may have noticed that up to this point, we've been discussing unchecked exceptions because they affect the logic of the application. In this chapter, we'll also be using unchecked exceptions, which signify errors in the logic of a method/application.

Creating Custom Exceptions

To create a custom exception in Java, you typically extend either Exception ( for checked exceptions ) or RuntimeException ( for unchecked exceptions ).

Steps to Create a Custom Exception:

Define a New Class: Your exception class should extend either Exception or RuntimeException, depending on whether you want it to be a checked or unchecked exception;
Constructor Overloading: Define constructors for your exception class. You can create multiple constructors to pass different types of information about the exception ( e.g., a simple message or another throwable cause ).

Example of a Custom Checked Exception:

CustomCheckedException.java

Example of a Custom Unchecked Exception:

CustomUncheckedException.java

Practice

Now, let's practice a bit and create our own exception, which will be used when the user is not of the required age to buy something in an online store. This exception should have a name that represents the error it indicates.
For example, NotOfLegalAgeException or PurchaseProhibitedException.

Note
This exception will be unchecked because such an error violates the program's logic.

Now, we can use this exception in our code and throw it in methods. Let's write a method that checks the user's age and throws an exception if they are younger than 21 years old.

main.java

Code Description

This code snippet represents a simple model of an online shopping service. It includes classes to manage user details, perform age checks for purchases, and handle a specific type of runtime exception related to purchase restrictions. Here's a step-by-step explanation of what each part of the code does:

Class: `User`

Purpose: Represents a user of the internet shop.

Attributes:

- email: A string storing the user's email.
- name: A string storing the user's name.
- properties: A string to store additional properties of the user.
- age: An integer representing the user's age.

Constructor:

- Initializes a User object with provided email, name, properties, and age.

Method - getAge:

- Returns the age of the user.

Class: `InternetShopService`

Purpose: Provides services related to the internet shop, such as age verification and ordering items.

Method - checkAge:

- Takes a User object and an integer requiredAge.
- Returns true if the user's age is greater than or equal to requiredAge, false otherwise.

Method - order:

- Allows a User to order an item if they meet the requiredAge.
- First, it checks the user's age using the checkAge method.
- If checkAge returns true (user is old enough), it prints "Ordered successfully!".
- If checkAge returns false, it throws a PurchaseProhibitedException with a message indicating that the user cannot buy the item until they reach the required age.
- There's a comment indicating a place for database operations, presumably for processing the order.

Class: `PurchaseProhibitedException`

Purpose: A custom exception class extending RuntimeException.

Constructor:

- Takes a string message and passes it to the superclass (RuntimeException) constructor. This message typically contains details about why the exception is thrown (e.g., user not being old enough to make the purchase).

As you can see, we're using the exception we created inside the code. Now, all that's left is to handle this exception when the method that throws it is called and print the exception message to the console. We will do this, of course, using a try-catch structure.

main.java

Now you can create your own custom exceptions and throw them in your code. Excellent!

1. What are the two main types of exceptions in Java?

2. When creating a custom checked exception, which class should it extend?

3. What is a key characteristic of unchecked exceptions in Java?

4. In the provided example, what is the purpose of the `PurchaseProhibitedException` class?

5. What does the `super(message)` call in the constructor of `PurchaseProhibitedException` do?

What are the two main types of exceptions in Java?

Selecciona la respuesta correcta

Logical Exceptions and Runtime Exceptions

Checked Exceptions and Unchecked Exceptions

Internal Exceptions and External Exceptions

When creating a custom checked exception, which class should it extend?

Selecciona la respuesta correcta

RuntimeException

Exception

Error

What is a key characteristic of unchecked exceptions in Java?

Selecciona la respuesta correcta

They must be declared in the method signature

They are checked at compile-time

They usually indicate programming errors, such as logic mistakes

In the provided example, what is the purpose of the PurchaseProhibitedException class?

Selecciona la respuesta correcta

To handle database errors in an online store

To indicate that a user is not of the required age to make a purchase

To manage user login and authentication

What does the super(message) call in the constructor of PurchaseProhibitedException do?

Selecciona la respuesta correcta

Calls the constructor of the superclass with the message

Creates a new instance of RuntimeException

Logs the error message to the console

¿Todo estuvo claro?

Sección 3. Capítulo 5

Contenido del Curso

Java JUnit Library. Types of Testing

1. Testing in Development

What is Testing, and Why do We Need It Types of Testing Application Stages Unit Testing Integration Testing Functional Testing Section 1 Summary

2. Unit Tests

Set-Up Test-Driven Development Creating Unit Tests @BeforeEach How to Test `void` Methods Assertions Assertions Practice Section 2 Summary

3. Exceptions

Throwing Exceptions Try-catch structure Handling Multiple Exceptions Handling Exceptions Practice Creating Exceptions Testing Exceptions Testing Exceptions Practice

Java JUnit Library. Types of Testing

Creating Exceptions

It's time to move on to creating your own custom exceptions that you can throw in your programs. First, it's important to note that there are two types of exceptions.

Types of Exceptions in Java

Checked Exceptions: These are exceptions that must be either caught or declared in the method signature. They are checked at compile-time.
Example: IOException;
Unchecked Exceptions: These exceptions are not checked at compile time. They usually indicate programming errors, such as logic mistakes or incorrect API usage.
Example: NullPointerException.

Note
You may have noticed that up to this point, we've been discussing unchecked exceptions because they affect the logic of the application. In this chapter, we'll also be using unchecked exceptions, which signify errors in the logic of a method/application.

Creating Custom Exceptions

To create a custom exception in Java, you typically extend either Exception ( for checked exceptions ) or RuntimeException ( for unchecked exceptions ).

Steps to Create a Custom Exception:

Define a New Class: Your exception class should extend either Exception or RuntimeException, depending on whether you want it to be a checked or unchecked exception;
Constructor Overloading: Define constructors for your exception class. You can create multiple constructors to pass different types of information about the exception ( e.g., a simple message or another throwable cause ).

Example of a Custom Checked Exception:

CustomCheckedException.java

Example of a Custom Unchecked Exception:

CustomUncheckedException.java

Practice

Note
This exception will be unchecked because such an error violates the program's logic.

Now, we can use this exception in our code and throw it in methods. Let's write a method that checks the user's age and throws an exception if they are younger than 21 years old.

main.java

Code Description