j.u.BitSet::stream

[Anonymous]

j.u.BitSet::stream

Is there already a helper in the StreamSupport? I failed to find one.
Or a plan to back-port it? Or a more clever / concise work-around?
Current work-around:

j8.u.s.IntStreams
        .range(0, bitSet.length())
        .filter(bitSet::get);

Or a more convoluted one:

j8.u.s.IntStreams
        .iterate(bitSet.nextSetBit(0), i -> bitSet.nextSetBit(i + 1))
        .takeWhile(i -> 0 <= i); // && i <= Integer.MAX_VALUE

/~Karel~/

[Stefan Zobel]

No, only Collections are supported. I had to draw a line somewhere. And BitSet.stream() being useful seems to be a very rare event.

I don't think that there is way to do better than you already did. Your first workaround looks quite reasonable to me.

[Anonymous]

BitSet::stream might be a pretty rare case, I agree — I wouldn't stumble upon it were I not porting Stream of Permutations [Java Precisely, p. 139, ex. 175]. I just got misled at first by the BitSet::toLongArray's doc saying: "Returns a new long array containing all the bits in this bit set." to a naïve & incorrect:

j8.u.s.LongStreams
        .of(bitSet.toLongArray())
        .mapToInt(l -> (int) l)

Since the long[] returned forms in fact a bit-packed internal storage of the set, instead of ordinal positions of bits set to true as in the case of BitSet::stream.

The line has to be drawn somewhere, indeed. Most of the time, it's sufficiently painless to go via T -> U[] -> Stream<U> or via T -> Collection<U> -> Stream<U>. Exceptions are scarce and usually require a range() + map(), like in:

j8.u.s.IntStreams
        .range(0, charSequence.length())
        .map(charSequence::charAt)

/~Karel~/

P.S.: Thank you very much for such a great lib! I'm using the streamsupport + retrolambda combo in a conservative (J6) production environment for about a half a year now and it helps immensely — sanity-wise! ;o)

[Stefan Zobel]

Hi Karel,

thanks for your kind words.

Nice to hear of a usage on Java 6! Sometimes I'm led to believe that streamsupport is mostly utilized by Android devs. Initially, Java 6 & Java 7 were the only target platforms I could imagine.

Cheers,
Stefan