returns a function that extracts the key of a map.entry . concode_field_sep String CONSTANT_KEY concode_field_sep DistributedFunction<T,T> wholeItem concode_elem_sep DistributedConsumer<T> noopConsumer concode_elem_sep DistributedPredicate<T> alwaysFalse concode_elem_sep DistributedFunction<Entry<K,V>,V> entryValue concode_elem_sep DistributedPredicate<T> alwaysTrue concode_elem_sep DistributedFunction<T,String> constantKey
DistributedFunction < Entry < K , V > , K > function ( ) { return Map . Entry :: getKey ; }