The key to customizing Java exceptions is to understand the inheritance structure and select the type reasonably. 1. Identify the exception type: If the caller needs to be forced to handle it, inherit Exception (checked exception); if it is a runtime error, inherit RuntimeException (non-checked exception). 2. When creating a custom exception class, you should provide no parameters, string parameters and constructors with exception reasons to ensure availability. 3. In the project, it should be properly thrown at business logic key points, such as login failure, verification failure, etc., and a unified response should be combined with global exception handling. At the same time, note that the detected exception needs to be declared try-catch or throws. 4. Avoid over-customization and prioritize reusing standard exceptions such as IllegalArgumentException, which are only customized when they cannot be accurately described to improve code clarity and maintainability.
It is actually not difficult to customize exceptions in Java. The key is to understand the inheritance structure of the exception class and choose whether to inherit Exception or RuntimeException according to your needs. Let’s talk about how to do it from a few practical perspectives.
1. Identify your exception type: tested or not tested?
Java exceptions are divided into two categories: checked exceptions and unchecked exceptions.
- If you want the caller to have to handle this exception, let it inherit
Exception. - If it is only used for runtime errors and does not require forced capture or declaration throwing, then inherit
RuntimeException.
For example: You are developing a tool class. If an illegal parameter is passed in a method, a runtime exception can be thrown; and if you are dealing with file reading failures, you usually need a checked exception.
2. Create the basic structure of a custom exception class
Creating a custom exception class is very simple. Generally, you only need to write one class, inherit the appropriate parent class, and provide several constructors.
for example:
public class InvalidUserInputException extends Exception {
public InvalidUserInputException() {
super();
}
public InvalidUserInputException(String message) {
super(message);
}
public InvalidUserInputException(String message, Throwable cause) {
super(message, cause);
}
}This way you can use it in your code:
if (input == null) {
throw new InvalidUserInputException("Input cannot be empty");
}3. Use it reasonably in actual projects
Custom exceptions are not added casually, their significance lies in clearly expressing exceptions in business logic . for example:
- throws a custom exception when user login fails
InvalidCredentialsException - Throw
ValidationFailedExceptionwhen data verification fails
These exceptions can be handled uniformly in the global exception handler and returned to the front-end more friendly error message.
Also, don't forget to use it in combination with try-catch or throws:
- If it is a checked exception, either catch or declare throws on the method
- Unchecked exceptions can be thrown directly without explicit processing
4. Don't over-customize
Although custom exceptions are very useful, don't create a new class for every small problem. In some cases, it is enough to directly reuse the standard library exception, such as:
-
IllegalArgumentException: The parameters are not appropriate -
IllegalStateException: The status is incorrect -
UnsupportedOperationException: The operation is not supported
Consider customization only if these standard exceptions cannot accurately describe your business scenario.
Basically that's it. Custom exceptions are not complicated in themselves, but using them well can make the code clearer and easier to maintain.
The above is the detailed content of How to create a custom exception in Java?. For more information, please follow other related articles on the PHP Chinese website!
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