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Shuffling a JSON array in Java



The 2019 Stack Overflow Developer Survey Results Are InSimplification of byte array comparison algorithmShuffling an array of cardsShuffling a deckShuffling array elements in CShuffling a list of track indicesLogic for shuffling sliding puzzleShuffling chunks of ints in an arrayBasic Pong GameJava Market Summary - JSONShuffling an array keeping some elements fixed





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$begingroup$


Since I did not get a satisfactory answer here (and I really needed to get it going on this weekend), I decided to implement my own Fisher–Yates shuffle, porting the code I found in other SO posts. I know my programming technique is far from optimal, so I decided to post this here.



What do you think? Can it be improved?



public static JSONArray shuffleJsonArray (JSONArray array) throws JSONException {

    // Implementing Fisher–Yates shuffle

        Random rnd = new Random();

        for (int i = array.length() - 1; i >= 0; i--)

        {

          int j = rnd.nextInt(i + 1);

          // Simple swap

          Object object = array.get(j);

          array.put(j, array.get(i));

          array.put(i, object);

        }

    return array;

}





java array json shuffle







share|improve this question











$endgroup$



















    2












    $begingroup$


    Since I did not get a satisfactory answer here (and I really needed to get it going on this weekend), I decided to implement my own Fisher–Yates shuffle, porting the code I found in other SO posts. I know my programming technique is far from optimal, so I decided to post this here.



    What do you think? Can it be improved?



    public static JSONArray shuffleJsonArray (JSONArray array) throws JSONException {
    
    // Implementing Fisher–Yates shuffle
    
        Random rnd = new Random();
    
        for (int i = array.length() - 1; i >= 0; i--)
    
        {
    
          int j = rnd.nextInt(i + 1);
    
          // Simple swap
    
          Object object = array.get(j);
    
          array.put(j, array.get(i));
    
          array.put(i, object);
    
        }
    
    return array;
    
}





    java array json shuffle







    share|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      Since I did not get a satisfactory answer here (and I really needed to get it going on this weekend), I decided to implement my own Fisher–Yates shuffle, porting the code I found in other SO posts. I know my programming technique is far from optimal, so I decided to post this here.



      What do you think? Can it be improved?



      public static JSONArray shuffleJsonArray (JSONArray array) throws JSONException {
      
    // Implementing Fisher–Yates shuffle
      
        Random rnd = new Random();
      
        for (int i = array.length() - 1; i >= 0; i--)
      
        {
      
          int j = rnd.nextInt(i + 1);
      
          // Simple swap
      
          Object object = array.get(j);
      
          array.put(j, array.get(i));
      
          array.put(i, object);
      
        }
      
    return array;
      
}





      java array json shuffle







      share|improve this question











      $endgroup$




      Since I did not get a satisfactory answer here (and I really needed to get it going on this weekend), I decided to implement my own Fisher–Yates shuffle, porting the code I found in other SO posts. I know my programming technique is far from optimal, so I decided to post this here.



      What do you think? Can it be improved?



      public static JSONArray shuffleJsonArray (JSONArray array) throws JSONException {
      
    // Implementing Fisher–Yates shuffle
      
        Random rnd = new Random();
      
        for (int i = array.length() - 1; i >= 0; i--)
      
        {
      
          int j = rnd.nextInt(i + 1);
      
          // Simple swap
      
          Object object = array.get(j);
      
          array.put(j, array.get(i));
      
          array.put(i, object);
      
        }
      
    return array;
      
}





      java array json shuffle




      java array json shuffle






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Jul 4 '17 at 3:35









      Jamal♦

      30.6k11121227




      30.6k11121227










      asked Apr 4 '11 at 6:08









      AleadamAleadam

      11315




      11315






















          1 Answer
          1






          active

          oldest

          votes


















          2












          $begingroup$

          It runs in $O(n)$ time so I'm not sure there's a way to improve this. It looks like you've implemented the algorithm pretty well, according the Fisher-Yates shuffle.



          You might consider not using Object if you can use the type that's stored in the array instead.



          I also thought I read somewhere that it should be safe to loop to $n/2$ instead of $n$ (because you're swapping with elements from $1 cdots n$ so in theory, you shouldn't need to swap every element), but I don't have hard proof of that, so you take your chances ;)






          share|improve this answer











          $endgroup$













          • $begingroup$
            Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
            $endgroup$
            – Aleadam
            Apr 4 '11 at 15:30










          • $begingroup$
            @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
            $endgroup$
            – FrustratedWithFormsDesigner
            Apr 4 '11 at 15:36












          • $begingroup$
            I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
            $endgroup$
            – leemes
            May 17 '12 at 20:58












          Your Answer





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          1 Answer
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          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          2












          $begingroup$

          It runs in $O(n)$ time so I'm not sure there's a way to improve this. It looks like you've implemented the algorithm pretty well, according the Fisher-Yates shuffle.



          You might consider not using Object if you can use the type that's stored in the array instead.



          I also thought I read somewhere that it should be safe to loop to $n/2$ instead of $n$ (because you're swapping with elements from $1 cdots n$ so in theory, you shouldn't need to swap every element), but I don't have hard proof of that, so you take your chances ;)






          share|improve this answer











          $endgroup$













          • $begingroup$
            Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
            $endgroup$
            – Aleadam
            Apr 4 '11 at 15:30










          • $begingroup$
            @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
            $endgroup$
            – FrustratedWithFormsDesigner
            Apr 4 '11 at 15:36












          • $begingroup$
            I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
            $endgroup$
            – leemes
            May 17 '12 at 20:58
















          2












          $begingroup$

          It runs in $O(n)$ time so I'm not sure there's a way to improve this. It looks like you've implemented the algorithm pretty well, according the Fisher-Yates shuffle.



          You might consider not using Object if you can use the type that's stored in the array instead.



          I also thought I read somewhere that it should be safe to loop to $n/2$ instead of $n$ (because you're swapping with elements from $1 cdots n$ so in theory, you shouldn't need to swap every element), but I don't have hard proof of that, so you take your chances ;)






          share|improve this answer











          $endgroup$













          • $begingroup$
            Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
            $endgroup$
            – Aleadam
            Apr 4 '11 at 15:30










          • $begingroup$
            @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
            $endgroup$
            – FrustratedWithFormsDesigner
            Apr 4 '11 at 15:36












          • $begingroup$
            I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
            $endgroup$
            – leemes
            May 17 '12 at 20:58














          2












          2








          2





          $begingroup$

          It runs in $O(n)$ time so I'm not sure there's a way to improve this. It looks like you've implemented the algorithm pretty well, according the Fisher-Yates shuffle.



          You might consider not using Object if you can use the type that's stored in the array instead.



          I also thought I read somewhere that it should be safe to loop to $n/2$ instead of $n$ (because you're swapping with elements from $1 cdots n$ so in theory, you shouldn't need to swap every element), but I don't have hard proof of that, so you take your chances ;)






          share|improve this answer











          $endgroup$



          It runs in $O(n)$ time so I'm not sure there's a way to improve this. It looks like you've implemented the algorithm pretty well, according the Fisher-Yates shuffle.



          You might consider not using Object if you can use the type that's stored in the array instead.



          I also thought I read somewhere that it should be safe to loop to $n/2$ instead of $n$ (because you're swapping with elements from $1 cdots n$ so in theory, you shouldn't need to swap every element), but I don't have hard proof of that, so you take your chances ;)







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 5 hours ago









          esote

          3,02611241




          3,02611241










          answered Apr 4 '11 at 15:15









          FrustratedWithFormsDesignerFrustratedWithFormsDesigner

          484210




          484210












          • $begingroup$
            Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
            $endgroup$
            – Aleadam
            Apr 4 '11 at 15:30










          • $begingroup$
            @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
            $endgroup$
            – FrustratedWithFormsDesigner
            Apr 4 '11 at 15:36












          • $begingroup$
            I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
            $endgroup$
            – leemes
            May 17 '12 at 20:58


















          • $begingroup$
            Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
            $endgroup$
            – Aleadam
            Apr 4 '11 at 15:30










          • $begingroup$
            @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
            $endgroup$
            – FrustratedWithFormsDesigner
            Apr 4 '11 at 15:36












          • $begingroup$
            I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
            $endgroup$
            – leemes
            May 17 '12 at 20:58
















          $begingroup$
          Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
          $endgroup$
          – Aleadam
          Apr 4 '11 at 15:30




          $begingroup$
          Thanks for looking at it. I based it on that wikipedia page and a couple of posts in SO. I will keep in mind the n/2 loops to change it if needed. Lastly, I wrote it using JSONObject instead of Object but then I changed it to make it more reusable. What would be the advantage of using JSONObject instead?
          $endgroup$
          – Aleadam
          Apr 4 '11 at 15:30












          $begingroup$
          @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
          $endgroup$
          – FrustratedWithFormsDesigner
          Apr 4 '11 at 15:36






          $begingroup$
          @Aleadam: I don't know the JSONArray datatype well, I guess I was trying to suggest to use Java generics so you don't have to use Object, but I don't know if you can do that with JSONArray.
          $endgroup$
          – FrustratedWithFormsDesigner
          Apr 4 '11 at 15:36














          $begingroup$
          I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
          $endgroup$
          – leemes
          May 17 '12 at 20:58




          $begingroup$
          I also think that there is no faster way for shuffling an array. Every try in doing it faster (O(log n) or O(sqrt n)) would result in a poorly shuffled array.
          $endgroup$
          – leemes
          May 17 '12 at 20:58


















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