How to use java.imports.groups?

[XuPengfei-1020]

How to present static import items (eg: ["org", "java", "static"])?
How to make a separator empty line between tow groups (or make there is no separator empty line between them)?
How to present other groups which not specified in the configuration (eg: ["org", "java", "others(alphabetic-order)"], how to present 'others')?

It there a documention of the grammar?

Thanks a lot!