release 6 is not found in the system
If you are facing the build error of The project was not built due to "release 6 is not found in the system". Fix the problem, then try refreshing this project and building it since it may be inconsistent in Eclipse, you can try the following steps and it works for me!
Build Error #
This error was happened when I was checking out the PDFBox svn branch on my MacBook and imported into the Eclipse IDE.

Solution #
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Right-click your selected project and click
Properties -
Go to the
Java Compilersettings -
Force Eclipse to prompt the
The compiler settings have changed. Rebuild the project to apply the changesmessage by doing nothing (select and deselect)
-
Click
Yesto apply your compiler settings -
Clean the project and enjoy