tokenStream
Creates the TokenStream used for indexing this field. If appropriate, implementations should use the given Analyzer to create the TokenStreams.
Return
TokenStream value for indexing the document. Should always return a non-null value if the field is to be indexed
Parameters
analyzer
Analyzer that should be used to create the TokenStreams from
reuse
TokenStream for a previous instance of this field name. This allows custom field types (like StringField and NumericField) that do not use the analyzer to still have good performance. Note: the passed-in type may be inappropriate, for example if you mix up different types of Fields for the same field name. So it's the responsibility of the implementation to check.