question: public DateTimeFormatterBuilder parseDefaulting ( TemporalField field , long value ) { Objects . requireNonNull ( field , "field" ) ; appendInternal ( new DefaultValueParser ( field , value ) ) ; return this ; }
target:  Appends a default value for a field to the formatter for use in parsing. <p> This appends an instruction to the builder to inject a default value into the parsed result. This is especially useful in conjunction with optional parts of the formatter. <p> For example, consider a formatter that parses the year, followed by an optional month, with a further optional day-of-month. Using such a formatter would require the calling code to check whether a full date, year-month or just a year had been parsed. This method can be used to default the month and day-of-month to a sensible value, such as the first of the month, allowing the calling code to always get a date. <p> During formatting, this method has no effect. <p> During parsing, the current state of the parse is inspected. If the specified field has no associated value, because it has not been parsed successfully at that point, then the specified value is injected into the parse result. Injection is immediate, thus the field-value pair will be visible to any subsequent elements in the formatter. As such, this method is normally called at the end of the builder.