What are the common causes of ClassNotFoundException exceptions in Java?

ClassNotFoundException exception in Java is one of the common problems in development. In Java development, it is a very common practice to obtain an instance of a class through the class name, but if the class to be loaded is not found, a ClassNotFoundException exception will be thrown. So, what are the common causes of ClassNotFoundException exceptions?

1. The class path is incorrect

In Java, when a class needs to be loaded, the JVM will search for the class in the class path. If the class path is specified incorrectly, or the class is not found in the class path, a ClassNotFoundException exception will be thrown. Common reasons include:

(1) Class path setting error: Sometimes developers may set the wrong class path, causing the JVM to be unable to find the required classes.

(2) Class file loss: If the class file of a certain class is accidentally deleted or moved, the JVM cannot find the class, thus throwing a ClassNotFoundException exception.

2. Class name error

ClassNotFoundException exception may also be caused by a spelling error in the class name or an error in the package name. If the class name or package name is incorrect, the JVM cannot find the class correctly.

3. The class is not loaded

If the class is not loaded correctly, a ClassNotFoundException exception will be thrown. Possible reasons include:

(1) JVM crash or abnormal termination: In some cases, the JVM will crash or terminate abnormally, causing some classes to not be loaded correctly.

(2) Incorrect class version: If the version of a class does not match the current class loader, or the versions of other classes that the class depends on are incorrect, then the class cannot be loaded correctly, thus throwing ClassNotFoundException abnormal.

In short, common causes of ClassNotFoundException include incorrect class path, wrong class name, and class not being loaded correctly. If you encounter this exception, you should investigate according to the specific situation, find out the cause of the exception, and make corresponding repairs.

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