How to throw exception in Java?
Throw an exception through the throw keyword, syntax: throw new ExceptionName(message). Steps: 1. Check the condition; 2. If the condition is not met, throw an exception: throw new ExceptionName(message); 3. Define a custom exception: inherit Exception and provide the constructor and getMessage() method.
How to throw exceptions in Java
In Java, you can throw exceptions through the throw
keyword abnormal. An exception is an event that indicates that a program has encountered a problem that prevents it from continuing to execute normally.
Syntax
throw new ExceptionName(message);
Where:
ExceptionName
is the class name to throw an exception.message
is an optional exception message that provides detailed information about the exception.
Practical case
Suppose we have a method to check whether the username is valid. If the username is invalid, we need to throw an exception to indicate the error.
public static void checkUsername(String username) throws InvalidUsernameException { // 检查用户名是否有效 if (username == null || username.isEmpty()) { throw new InvalidUsernameException("用户名不能为空"); } }
When calling the checkUsername
method, if the incoming username is invalid, an InvalidUsernameException
exception will be thrown.
Custom exceptions
Java provides a Exception
base class for all exceptions. However, we can also create our own custom exception classes to provide more detailed information for specific types of errors.
Here are the steps to create a custom exception InvalidUsernameException
:
- Create a new class that inherits from
Exception
. - Provide a constructor to receive exception messages.
- Redefine the
getMessage()
method as needed.
public class InvalidUsernameException extends Exception { public InvalidUsernameException(String message) { super(message); } }
Using Custom Exceptions
Custom exceptions can be thrown and handled in the same way as built-in exceptions.
try { checkUsername("admin"); } catch (InvalidUsernameException e) { System.out.println(e.getMessage()); }
Best Practices
- Throw only exceptions that may actually affect program execution.
- Develop a clear exception handling strategy to ensure that exceptions are handled correctly.
- Use custom exceptions to provide more details about specific errors.
The above is the detailed content of How to throw exception in Java?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics



Guide to Perfect Number in Java. Here we discuss the Definition, How to check Perfect number in Java?, examples with code implementation.

Guide to Weka in Java. Here we discuss the Introduction, how to use weka java, the type of platform, and advantages with examples.

Guide to Smith Number in Java. Here we discuss the Definition, How to check smith number in Java? example with code implementation.

In this article, we have kept the most asked Java Spring Interview Questions with their detailed answers. So that you can crack the interview.

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

Guide to TimeStamp to Date in Java. Here we also discuss the introduction and how to convert timestamp to date in java along with examples.

Capsules are three-dimensional geometric figures, composed of a cylinder and a hemisphere at both ends. The volume of the capsule can be calculated by adding the volume of the cylinder and the volume of the hemisphere at both ends. This tutorial will discuss how to calculate the volume of a given capsule in Java using different methods. Capsule volume formula The formula for capsule volume is as follows: Capsule volume = Cylindrical volume Volume Two hemisphere volume in, r: The radius of the hemisphere. h: The height of the cylinder (excluding the hemisphere). Example 1 enter Radius = 5 units Height = 10 units Output Volume = 1570.8 cubic units explain Calculate volume using formula: Volume = π × r2 × h (4

Java is a popular programming language that can be learned by both beginners and experienced developers. This tutorial starts with basic concepts and progresses through advanced topics. After installing the Java Development Kit, you can practice programming by creating a simple "Hello, World!" program. After you understand the code, use the command prompt to compile and run the program, and "Hello, World!" will be output on the console. Learning Java starts your programming journey, and as your mastery deepens, you can create more complex applications.
