Completed testGetContactsString() JUnit test. It passes.
Tried and failed to work out how to test flush() and XMLDecoder in
JUnit.
Pushing it all up now, possibly for last time. Visibilities changed due
to JUnit test are all returned, i.e. all private methods back from
public. Returned private visibilities to ContactManagerImpl's member
fields. (Hence JUnit tests' compiler issues are entirely due to this).