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Groups > comp.lang.java.programmer > #32740

Re: parallel stream with return

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On 09/30/2015 02:35 AM, Philipp Kraus wrote:
> Hello,
>
> I'm new with the Java 1.8 parallel stream, so I have got a problem:
>
> I have the sequential for loop:
>
> final Set<myClass> x = new HashSet<>();
> for(int i=0; i < value; ++i)
>      x.add( this.generate() );
>
> And I would like to do this with a parallel stream which collects each generate return value into the set.
> My first try was to use a synchronized HashSet and
>
> IntStream.range(0, value).parallel().forEach( i-> { x.add(this.generate()) } );
>
> After that I try to swap forEach to map, but at this I must return an int value and not a myClass value, so how can I do n generate calls in parallel and collect the results into a hashset?
>
What's wrong with what you had to start?
Have I misunderstood?

import java.util.HashSet;
import java.util.stream.IntStream;

public class Scratch {

   private final int count;
   private final String name;

   private Scratch(int i, String t) { count = i; name = t;}

   public static void main(String[] args) {
     HashSet<Scratch> x = new HashSet<>();
     IntStream.range(0, 4096).parallel()
       .forEach(i -> { x.add(generate(i)); });
     for (Scratch s : x) {
       System.out.println(s.count + " : " + s.name);
     }
   }

   private static Scratch generate(int i) {
     return new Scratch(i, Thread.currentThread().getName());
   }

}

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Thread

parallel stream with return Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-09-29 23:35 -0700
  Re: parallel stream with return Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-09-30 08:01 -0400
    Re: parallel stream with return Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-09-30 08:02 -0700
      Re: parallel stream with return Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-09-30 13:22 -0400
        Re: parallel stream with return Steven Simpson <ss@my.domain.invalid> - 2015-09-30 22:25 +0100
  Re: parallel stream with return Jeff Higgins <jeff@invalid.invalid> - 2015-09-30 16:41 -0400
    Re: parallel stream with return Jeff Higgins <jeff@invalid.invalid> - 2015-09-30 16:53 -0400
      Re: parallel stream with return Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2015-09-30 23:36 -0700
        Re: parallel stream with return Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-01 08:22 -0400
        Re: parallel stream with return Jeff Higgins <jeff@invalid.invalid> - 2015-10-01 08:54 -0400

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