add newline after autoformat java codeblock

[danthe1st]

When code is autoformatted, the (detected) codeblock section is added immediately after ```java. If that section starts with an alphanumeric character, this results in the language identifier (java) being merged with the first word, e.g. javapublic instead of public with Java formatting.

This PR adds a line break after the ```java in order to avoid this issue.