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Groups > comp.lang.java.programmer > #8587

Re: DataInputStream

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On 10/5/2011 10:17 AM, bob wrote:
> The issue is that it's too slow.
>
> What I'm hoping for is something like this:
>
> 			byte[] b = new byte[numfloats*4];
> 			dis.read(b, 0, numfloats*4);
> 			float[] f = (float[]) b;
> 			return f;
>
> I don't know why, but it won't let me do the cast.  Any ideas?

     "Why" is because an array of byte is not an array of float.
Objects in Java (an array is an object) are not just blobs of
memory; they have more identity, more selfhood.

     The wider problem you seem to be struggling with is that
reading these numbers is "slow as molasses" (as you so precisely
put it in a related thread).  Several people have suggested that
you (a) refine your notions of slowness and (b) take various
steps to determine what contributes to it.  As far as I can see
you've done neither: You're simply assuming (on no basis that's
been revealed) that the process of assembling bytes into floats is
the fount of treacle.  That's conceivable, just, but strikes me as
highly unlikely.  Go, and sin no more: Make some measurements of
where the time goes, and attack the measured hot spots instead of
your imagined phantoms.

-- 
Eric Sosman
esosman@ieee-dot-org.invalid

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DataInputStream bob <bob@coolgroups.com> - 2011-10-04 22:34 -0700
  Re: DataInputStream Robert Klemme <shortcutter@googlemail.com> - 2011-10-05 08:02 +0200
    Re: DataInputStream bob <bob@coolgroups.com> - 2011-10-04 23:17 -0700
      Re: DataInputStream Robert Klemme <shortcutter@googlemail.com> - 2011-10-05 00:07 -0700
        Re: DataInputStream bob <bob@coolgroups.com> - 2011-10-05 07:17 -0700
          Re: DataInputStream markspace <-@.> - 2011-10-05 08:27 -0700
          Re: DataInputStream Patricia Shanahan <pats@acm.org> - 2011-10-05 08:38 -0700
          Re: DataInputStream Robert Klemme <shortcutter@googlemail.com> - 2011-10-05 08:58 -0700
            Re: DataInputStream Lew <lewbloch@gmail.com> - 2011-10-05 14:52 -0700
              Re: DataInputStream Patricia Shanahan <pats@acm.org> - 2011-10-05 15:15 -0700
              Re: DataInputStream Robert Klemme <shortcutter@googlemail.com> - 2011-10-06 00:11 -0700
                Re: DataInputStream Lew <lewbloch@gmail.com> - 2011-10-06 07:08 -0700
                Re: DataInputStream Patricia Shanahan <pats@acm.org> - 2011-10-06 07:49 -0700
          Re: DataInputStream Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-05 21:16 -0400
      Re: DataInputStream Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-10-05 08:12 +0000
        Re: DataInputStream bob <bob@coolgroups.com> - 2011-10-05 07:12 -0700
  Re: DataInputStream Roedy Green <see_website@mindprod.com.invalid> - 2011-10-06 02:48 -0700

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