Compilation under JDK11

[sramazzina]

Just made some changes to have the code compiling under JDK 11 (see issue #44) . I hope you find it interesting and you will merge it. Let me know in case of any questions

Notes for Reviewers

• [ ] The commit history must be preserved - please use the rebase-merge or standard merge option instead of squash-merge
• [ ] Sync up with the author before merging

[CLAassistant]

All committers have signed the CLA.

[bernd]

@sramazzina Thanks for the PR! What's the reason for bumping the required Java version from 7 to 11? Can we compile with 11 (and newer) without this breaking change?