What is the meaning of the error message "IllegalArgumentException: 'input == null!'" thrown by java's getResourceAsStream()?

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This error message means that the input parameter passed to the getResourceAsStream() method is null. The method is designed to read a resource file from the classpath as an input stream, but it requires a valid resource name to be passed as the input parameter. If the input parameter is null, the method cannot read the resource file and throws this exception.