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Make sure the file resides in the project folder if you're referencing it via a relative path. If not, use the absolute path to the file with the file extension.
Use the relative path when providing the location of the file. Place the file in the project folder and access it according to the hierarchy. If you want to access a file outside the project folder, provide the absolute path.
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java.io.FileNotFoundException: document.pdf (No such file or directory)
at java.io.FileInputStream.open(Native Method)