Java never die

I get build errors in netbeans editor and project view now, although when I Clean Build the project I get Build successful in the output log.

Whose fault is it? I don’t know.

What to do? Open <your project> properties –> Sources and ensure that source format is the same
as jdk you [...]

Maven says: “The plugin does not exist or no valid version could be found”, but plugin present in your local repository.
Whose fault is it? I don’t know.
What to do? Try to delete plugin from local repository in order to enforce Maven to download it again.