Fixed a couple of deprecation warnings

[StefanSpieker]

Fixed a couple of deprecation warnings, including:

• using ACL.SYSTEM2 instead of deprecated ACL.SYSTEM
• using OutputStream.nullOutputStream()
• using TemporaryFolder instead of deprecated j.createTmpDir()
• some raw use of parameterized class

Testing done

All tests keep passing locally, the changes should not change anything.

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