[MJAVADOC-759] protected static --> static in JavadocUtil

**[Elliotte Rusty Harold](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=elharo)** opened **[MJAVADOC-759](https://issues.apache.org/jira/browse/MJAVADOC-759?redirect=false)** and commented

JavadocUtil is essentially a static utility class that should not be instantiated or subclassed. However it has many protected static methods that likely should have been package protected (default access) instead.

If we can stomach the minor API breakage of hiding these methods, that makes some other changes like moving to the Tool Provider API simpler.

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No further details from [MJAVADOC-759](https://issues.apache.org/jira/browse/MJAVADOC-759?redirect=false)

Start by locating JavadocUtil and reviewing its protected static methods and their callers. Check the plugin's existing tests before changing access, and consider the API-breakage concern described in the issue. Done means the intended methods are package-protected and the existing test suite still passes.

Written by the indexing model from the issue text.