What are the possible causes of File.getAbsolutePath() returning null?

I'm running into a bug that appears to be caused by File.getAbsolutePath() returning null. What conditions could cause this? 开发者_JAVA百科 (The system seeing the exception is running Windows XP.)

The javadoc has a brief description of the path resolution procedure, but doesn't mention any situation that would result in a null path string being returned.

The obvious I suppose -- When the file is not instantiated or doesn't exist

Tracing through the API classes, the answer should be in Win32FileSystem.resolve(File) (look in your src.zip file)

You could always copy/paste the code from this method into your own project and then step through it with the File that's causing the problem.