limit public API to enhance evolvability in future

[elharo]

and small Javadoc improvements

@garydgregory

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d57f3c7) 85.90% compared to head (f657bc5) 85.92%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #538      +/-   ##
============================================
+ Coverage     85.90%   85.92%   +0.02%     
- Complexity     3474     3475       +1     
============================================
  Files           230      230              
  Lines          8229     8222       -7     
  Branches        964      961       -3     
============================================
- Hits           7069     7065       -4     
+ Misses          870      867       -3     
  Partials        290      290              

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[garydgregory]

Note: This PR is probably OK since Apache HBase does not appear to make use of these methods and I intend to create a PR to reuse this class in HBase as HBase already uses Commons IO.