Why does getClass().getResource() cause NullPointerExceptions in Eclipse and Command Line?

File Loading Issues with getClass().getResource() in Eclipse and Command Line

Loading resources using getClass().getResource() can be challenging when working with Eclipse and the command line, leading to null pointer exceptions. To resolve this issue, we need to understand how class loaders operate.

Classpath Issues

getClass().getResource() utilizes the class loader to locate resources. This implies that the resource must reside within the classpath to be accessible. When executing the program in Eclipse, the bin directory, which comprises compiled class files and resource files, is automatically added to the classpath. Therefore, the resource is successfully loaded.

However, when running the program from the command line, the bin directory is not included in the classpath by default. Consequently, the resource remains inaccessible, resulting in the null pointer exception.

Resource Loading Method

When loading resources, the following best practice should be adhered to:

getClass().getResourceAsStream("Test.properties")

This method ensures that the resource is retrieved using the class loader, which is compatible with both local file systems and other deployment scenarios such as JAR files or network loading.

By addressing the classpath issues and using the recommended resource loading method, we can effectively eliminate the null pointer exceptions encountered when loading resources using getClass().getResource().

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