@SuppressWarnings("rawtypes")
    public static <T> Collector<T, ?, Optional<T>> onlyOne() {
        final Supplier<Holder<Optional<T>>> supplier = (Supplier) onlyOne_supplier;
        final BiConsumer<Holder<Optional<T>>, T> accumulator = (BiConsumer) onlyOne_accumulator;
        final BinaryOperator<Holder<Optional<T>>> combiner = (BinaryOperator) onlyOne_combiner;
        final Function<Holder<Optional<T>>, Optional<T>> finisher = (Function) onlyOne_finisher;

        return new CollectorImpl<>(supplier, accumulator, combiner, finisher, CH_UNORDERED_NOID);
    }
@ SuppressWarnings ( "rawtypes" ) public static < T > Collector < T , ? , Optional < T > > onlyOne ( ) { final Supplier < Holder < Optional < T > > > supplier = ( Supplier ) onlyOne_supplier ; final BiConsumer < Holder < Optional < T > > , T > accumulator = ( BiConsumer ) onlyOne_accumulator ; final BinaryOperator < Holder < Optional < T > > > combiner = ( BinaryOperator ) onlyOne_combiner ; final Function < Holder < Optional < T > > , Optional < T > > finisher = ( Function ) onlyOne_finisher ; return new CollectorImpl < > ( supplier , accumulator , combiner , finisher , CH_UNORDERED_NOID ) ; }
{@code DuplicatedResultException} is threw if there are more than one values are collected.

@return