Design: Are BlendedInfixSuggester's LINEAR_COEF and DEFAULT_NUM_FACTOR fields intended to be mutable?

[paulirwin]

(Found during reviewing code while porting to the Lucene.NET project.)

BlendedInfixSuggester has two static, mutable fields that seem like they might have been intended to be constants instead: LINEAR_COEF and DEFAULT_NUM_FACTOR. We wanted to know whether it was intentional that these were mutable, or an oversight that should be corrected and both marked final.

DEFAULT_NUM_FACTOR does not seem to have much utility if it is modified, and could result in bugs if it is modified during execution. Perhaps there is good reasoning for modifying it, though, that could be documented on the field.

LINEAR_COEF seems like a possible use case for modifying it would be to change the algorithm's math, but if so it is unexpected then that it is protected instead of public.

Affects Lucene 4.7.0 through current (10.1.0).