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Thread: how to compare two set values

  1. #1
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    Default how to compare two set values

    Hi guys,

    I need to itterate through 2 sorted sets and compare the values in the set. These sets are of type String and are called listOfNames1 and listOfNames2. If they are not the same i need these values to be added to another set called different.

    The code I have is below. This works as I expect it to when i change if (names1 != names2) to if (names1 == names2) but when im trying to get it to add the names that are not the same it just adds all the names in listOfNames1 to the sortedSet different.



     public void notTheSame() 
       {
          SortedSet<String>different = new TreeSet<String>();
          for(String names1 : listOfNames1)
          {
             for(String names2 : listOfNames2)
             {
                if (names1 != names2)
                {
                   different.add(names1);
                }
             }return null;
          }

    Hope someone can help. thankyou in advance for anyone that takes the time to try.
    Last edited by humdinger; March 13th, 2010 at 09:16 AM.


  2. #2
    Super Moderator copeg's Avatar
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    Default Re: how to compare two set values

    There is an easier way to find similarities and differences between sets...look at The Set Interface (The Java™ Tutorials > Collections > Interfaces) and scroll down to the Bulk Operations where there are code listings for how to go about doing this. For example, to find the difference:
    Set<String> difference = new HashSet<String>(listOfNames1);
    difference.removeAll(listOfNames2);

  3. The Following User Says Thank You to copeg For This Useful Post:

    humdinger (March 13th, 2010)

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