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Thread: Java

  1. #1
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    Default Java

    Hi
    I have asked for a question that is we have a class named Student that has some fields like name,age and date of birth.
    i have to write a programm that can sort the list of students on the basis of his name,age and date of birth.
    if name is same than on the basis of age, if name and age are same then on the basis of date of birth.
    could anyone pls help me by giving the code for that?

    Thanks for help in advance.


  2. #2
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    Default Re: Java

    No, users here will not 'give you the code.' Start the program yourself and ask for help as you need it.

  3. #3
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    Default Re: Java

    Now giving the code:

    class Students
    {
     String name;
     int age;
     Date dob;
    }
     class  SortList
      {
       Student st;
      List <Students>  raw_sts=new Arraylist<Students>();
      List <Students>  sorted_sts=new Arraylist<Students>();
     
     
         public static void main(String arr[])
         {
              st=new Students();
             sorted_sts= Collections.sort(sts,st.name); //here i am little bit confuse what to give next to this line; that i want to be clarified.
                                                                       bcz it will sort on the basis of name only.rest condition would not be fullfilled.
     
       }
    }
    Last edited by jps; August 11th, 2013 at 09:52 AM. Reason: code tags

  4. #4
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    Default Re: Java

    Please post your code in code or highlight=java tags.

    Comments:

    The class is name 'Students', so the declaration should be "Students st;" (with an 's' at the end of Student).
    ArrayList is capital 'A', capital 'L'
    In order to use the variables st, raw_sts, and sorted_sts in the static method main(), the variables must be declared static.

    As for your sorting question, you may want to use Collections.sort() as you have already done (with corrected arguments), then look for those that have the same last names, sort those by age; then look for those with same last name and same age and sort those by DOB.

    To accomplish the sorting of the Students sub-Lists, you could write your own sorter from the start; write a sorter that handles the duplicate cases after the main sorting has been done; or identify the specific special cases (same last name, etc.), create a special sub-List of just those items, and reform/re-sort those using Collections.sort() or the other approach you've used for the main case.

    I don't have an opinion about which is easiest. I would be inclined to write my own sorter from the start or use Collections.sort() to do the heavy lifting and then augment those results with my own sorter, leaning towards the latter.

  5. #5
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    Default Re: Java

    Hello.
    You class Students can implement the java.util.Comparable interface and override the compareTo() method.
    In this method, write the logic based on your sorting requirements.
    Then you can invoke Collections.sort() or Arrays.sort() method.

    Syed.

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