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Random permutations [was Re: Libraries for sysadmins?]

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Am 04.03.2016 21:13, schrieb Stefan Ram:
[snip]
>
>    I like to investigate how to concisely write a program to print
>    numbers simulating the German lotto »6 from 49«, where six
>    numbers are chosen from 1..49 in different programming languages.
>
>    Here is my Java version:
>
> public class Main
> { public static void main( final java.lang.String[] args )
>    { final java.util.List<java.lang.Integer> numbers =
>      java.util.stream.IntStream.rangeClosed( 1, 49 ).boxed().
>      collect( java.util.stream.Collectors.toList() );
>      java.util.Collections.shuffle( numbers );
>      java.lang.System.out.println( numbers.subList( 0, 6 ) ); }}
>
[snip]

This is good if you need about as many elements in the result as are in 
the range. But if the range is large and you need only a few elements, 
it may be better to generate numbers (without duplicates), like this:

new Random().ints(1, 50).distinct().limit(6)

[Side note, not relevant to the lotto example: IntStream#distinct() uses 
a LinkedHashSet internally, so that the order is maintained, as required 
by the java docs for Stream#distinct().]

-- Sebastian

PS: Whoever taught you to qualify the name of classes from java.lang?

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Libraries for sysadmins? Elena <egarrulo@gmail.com> - 2016-03-04 03:33 -0800
  Re: Libraries for sysadmins? Martin Gregorie <martin@address-in-sig.invalid> - 2016-03-04 11:44 +0000
    Re: Libraries for sysadmins? egarrulo <egarrulo@gmail.com> - 2016-03-04 12:56 +0100
  Re: Libraries for sysadmins? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-03-04 07:43 -0500
  Re: Libraries for sysadmins? Robert Klemme <shortcutter@googlemail.com> - 2016-03-04 18:06 +0100
    Re: Libraries for sysadmins? egarrulo <egarrulo@gmail.com> - 2016-03-04 20:30 +0100
      Random permutations [was Re: Libraries for sysadmins?] Sebastian <news@seyweiler.dyndns.org> - 2016-03-05 00:56 +0100
        Re: Random permutations [was Re: Libraries for sysadmins?] Robert Klemme <shortcutter@googlemail.com> - 2016-03-05 12:11 +0100
          Re: Random permutations [was Re: Libraries for sysadmins?] Sebastian <news@seyweiler.dyndns.org> - 2016-03-05 16:41 +0100
            Re: Random permutations [was Re: Libraries for sysadmins?] Brixomatic <brixomatic@yahoo.com> - 2016-03-05 19:20 +0100
              Re: Random permutations [was Re: Libraries for sysadmins?] Andreas Leitgeb <avl@logic.at> - 2016-03-05 18:46 +0000
                Re: Random permutations [was Re: Libraries for sysadmins?] Brixomatic <brixomatic@yahoo.com> - 2016-03-15 19:22 +0100
                Re: Random permutations [was Re: Libraries for sysadmins?] Andreas Leitgeb <avl@logic.at> - 2016-03-15 22:30 +0000
            Re: Random permutations [was Re: Libraries for sysadmins?] Andreas Leitgeb <avl@logic.at> - 2016-03-05 18:30 +0000
              Re: Random permutations [was Re: Libraries for sysadmins?] Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-03-05 13:46 -0500
                Re: Random permutations [was Re: Libraries for sysadmins?] Andreas Leitgeb <avl@logic.at> - 2016-03-05 19:40 +0000
      Re: Libraries for sysadmins? Robert Klemme <shortcutter@googlemail.com> - 2016-03-05 12:10 +0100
    Re: Libraries for sysadmins? Arne Vajhøj <arne@vajhoej.dk> - 2016-03-04 21:42 -0500
  Re: Libraries for sysadmins? Arne Vajhøj <arne@vajhoej.dk> - 2016-03-04 21:48 -0500

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