Exception while sorting a list of objects based on date property(String type)



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0















I am trying to sort a list of Objects based on dates (In String). The dates are in string and the objects have date property value assigned "-" if there is no date with it.
I am doing the below code snippet to sort it however at one point it is giving me " Comparison method violates its general contract" exception. I am not able to figure out where the contract is breaking and how.



I looked into other threads but could not get much help.



Any inputs what could I be doing wrong?



Collections.sort(listOfObjects, new Comparator<ObjectType>()

@Override
public int compare(ObjectType objectOne, ObjectType objectTwo)
if(sortType.equalsIgnoreCase("asc"))
if(objectOne.getSomeDate().equalsIgnoreCase("-"))
return 1;
if(objectTwo.getDeliveryQueueResponseDTO().getSomeDate().equalsIgnoreCase("-"))
return -1;
sort = objectOne.getSomeDate().compareToIgnoreCase(objectTwo.getSomeDate());

else
sort = objectTwo.getSomeDate().compareToIgnoreCase(objectOne.getSomeDate());


return sort;










share|improve this question




























    0















    I am trying to sort a list of Objects based on dates (In String). The dates are in string and the objects have date property value assigned "-" if there is no date with it.
    I am doing the below code snippet to sort it however at one point it is giving me " Comparison method violates its general contract" exception. I am not able to figure out where the contract is breaking and how.



    I looked into other threads but could not get much help.



    Any inputs what could I be doing wrong?



    Collections.sort(listOfObjects, new Comparator<ObjectType>()

    @Override
    public int compare(ObjectType objectOne, ObjectType objectTwo)
    if(sortType.equalsIgnoreCase("asc"))
    if(objectOne.getSomeDate().equalsIgnoreCase("-"))
    return 1;
    if(objectTwo.getDeliveryQueueResponseDTO().getSomeDate().equalsIgnoreCase("-"))
    return -1;
    sort = objectOne.getSomeDate().compareToIgnoreCase(objectTwo.getSomeDate());

    else
    sort = objectTwo.getSomeDate().compareToIgnoreCase(objectOne.getSomeDate());


    return sort;










    share|improve this question
























      0












      0








      0








      I am trying to sort a list of Objects based on dates (In String). The dates are in string and the objects have date property value assigned "-" if there is no date with it.
      I am doing the below code snippet to sort it however at one point it is giving me " Comparison method violates its general contract" exception. I am not able to figure out where the contract is breaking and how.



      I looked into other threads but could not get much help.



      Any inputs what could I be doing wrong?



      Collections.sort(listOfObjects, new Comparator<ObjectType>()

      @Override
      public int compare(ObjectType objectOne, ObjectType objectTwo)
      if(sortType.equalsIgnoreCase("asc"))
      if(objectOne.getSomeDate().equalsIgnoreCase("-"))
      return 1;
      if(objectTwo.getDeliveryQueueResponseDTO().getSomeDate().equalsIgnoreCase("-"))
      return -1;
      sort = objectOne.getSomeDate().compareToIgnoreCase(objectTwo.getSomeDate());

      else
      sort = objectTwo.getSomeDate().compareToIgnoreCase(objectOne.getSomeDate());


      return sort;










      share|improve this question














      I am trying to sort a list of Objects based on dates (In String). The dates are in string and the objects have date property value assigned "-" if there is no date with it.
      I am doing the below code snippet to sort it however at one point it is giving me " Comparison method violates its general contract" exception. I am not able to figure out where the contract is breaking and how.



      I looked into other threads but could not get much help.



      Any inputs what could I be doing wrong?



      Collections.sort(listOfObjects, new Comparator<ObjectType>()

      @Override
      public int compare(ObjectType objectOne, ObjectType objectTwo)
      if(sortType.equalsIgnoreCase("asc"))
      if(objectOne.getSomeDate().equalsIgnoreCase("-"))
      return 1;
      if(objectTwo.getDeliveryQueueResponseDTO().getSomeDate().equalsIgnoreCase("-"))
      return -1;
      sort = objectOne.getSomeDate().compareToIgnoreCase(objectTwo.getSomeDate());

      else
      sort = objectTwo.getSomeDate().compareToIgnoreCase(objectOne.getSomeDate());


      return sort;







      java collections comparator






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 15 '18 at 17:29









      user3262365user3262365

      298




      298






















          2 Answers
          2






          active

          oldest

          votes


















          1














          You should implement correctly the comparison between to "-" (empty dates).



          If you don't you get that a="-" and b="-" you have that compare(a,b)==1 and compare(b,a)==1 so a>b and b>a which don't make sense.






          share|improve this answer























          • I figured it out. Thanks buddy.

            – user3262365
            Nov 15 '18 at 17:56


















          1














          It basically means your comparator is not transitive. For more details, look at this question:



          "Comparison method violates its general contract!"






          share|improve this answer























          • Can you point out in my code where it is not transitive?

            – user3262365
            Nov 15 '18 at 17:36











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          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1














          You should implement correctly the comparison between to "-" (empty dates).



          If you don't you get that a="-" and b="-" you have that compare(a,b)==1 and compare(b,a)==1 so a>b and b>a which don't make sense.






          share|improve this answer























          • I figured it out. Thanks buddy.

            – user3262365
            Nov 15 '18 at 17:56















          1














          You should implement correctly the comparison between to "-" (empty dates).



          If you don't you get that a="-" and b="-" you have that compare(a,b)==1 and compare(b,a)==1 so a>b and b>a which don't make sense.






          share|improve this answer























          • I figured it out. Thanks buddy.

            – user3262365
            Nov 15 '18 at 17:56













          1












          1








          1







          You should implement correctly the comparison between to "-" (empty dates).



          If you don't you get that a="-" and b="-" you have that compare(a,b)==1 and compare(b,a)==1 so a>b and b>a which don't make sense.






          share|improve this answer













          You should implement correctly the comparison between to "-" (empty dates).



          If you don't you get that a="-" and b="-" you have that compare(a,b)==1 and compare(b,a)==1 so a>b and b>a which don't make sense.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 15 '18 at 17:40









          minusminus

          1,8511113




          1,8511113












          • I figured it out. Thanks buddy.

            – user3262365
            Nov 15 '18 at 17:56

















          • I figured it out. Thanks buddy.

            – user3262365
            Nov 15 '18 at 17:56
















          I figured it out. Thanks buddy.

          – user3262365
          Nov 15 '18 at 17:56





          I figured it out. Thanks buddy.

          – user3262365
          Nov 15 '18 at 17:56













          1














          It basically means your comparator is not transitive. For more details, look at this question:



          "Comparison method violates its general contract!"






          share|improve this answer























          • Can you point out in my code where it is not transitive?

            – user3262365
            Nov 15 '18 at 17:36















          1














          It basically means your comparator is not transitive. For more details, look at this question:



          "Comparison method violates its general contract!"






          share|improve this answer























          • Can you point out in my code where it is not transitive?

            – user3262365
            Nov 15 '18 at 17:36













          1












          1








          1







          It basically means your comparator is not transitive. For more details, look at this question:



          "Comparison method violates its general contract!"






          share|improve this answer













          It basically means your comparator is not transitive. For more details, look at this question:



          "Comparison method violates its general contract!"







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 15 '18 at 17:35









          mjuarezmjuarez

          10.6k73954




          10.6k73954












          • Can you point out in my code where it is not transitive?

            – user3262365
            Nov 15 '18 at 17:36

















          • Can you point out in my code where it is not transitive?

            – user3262365
            Nov 15 '18 at 17:36
















          Can you point out in my code where it is not transitive?

          – user3262365
          Nov 15 '18 at 17:36





          Can you point out in my code where it is not transitive?

          – user3262365
          Nov 15 '18 at 17:36

















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