How to sort and get highest value from Java Object/ArrayList

Question

I have an ArrayList with Student Objects (Name, Mark in Math, Mark in Physics). How can I sort the ArrayList and edit with first highest number/s, then second highest then third and so on. For example I have the object value below:

ArrayList<> allStudents = new ArrayList();
allStudents.add(new Student("A", 80, 94) );
allStudents.add(new Student("B", 98, 91) );
allStudents.add(new Student("F", 70, 84) );
allStudents.add(new Student("C", 98, 92) );
allStudents.add(new Student("H", 99, 93) );

I will look for the student with highest number, I got H. I edit the object like: "H", 97, 90 and save it back to that ArraList. Again I look for 2nd highest but here I have students "B" and "C", I can see they same number in math but in Physics C has highest number so I will edit "C", 96, 90 and save it back to the ArrayList and so on. Here which student already edited, I will not fetch them for edit and save thr and so on. IF someone please help me! Thanks in advance

it sorted by bellow code, now if you please tell more about the next part written above? that is; which one will be edited, I will not get that one when search, since for some reason I will have to search the whole ArrayList again and again — logcat, Jun 04 '14 at 00:35
if you please look here and suggestme http://stackoverflow.com/questions/24028238/edit-object-arraylist-in-java-again-and-again — logcat, Jun 04 '14 at 02:58

score 3 · Answer 1 · answered Jun 03 '14 at 22:59

3

Implement a Comparable interface to your student object and specify how you want it to compare.

Here is a good example: http://www.mkyong.com/java/java-object-sorting-example-comparable-and-comparator/

answered Jun 03 '14 at 22:59

Marcus Gabilheri

1,259
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Rod_Algonquin · Accepted Answer · 2014-06-03T23:12:30.663

2

You need to create a Comparator it can be anonymous or a class and in your Student do a get method for your mark so you can use it inside the comparator to compare the marks for sorting

example:

ArrayList<Student> allStudents = new ArrayList();
        allStudents.add(new Student("A", 80, 94));
        allStudents.add(new Student("B", 98, 91));
        allStudents.add(new Student("F", 70, 84));
        allStudents.add(new Student("C", 98, 92));
        allStudents.add(new Student("H", 99, 93));

        Collections.sort(allStudents, new Comparator<Student>() {

            public int compare(Student s, Student s2) {
                return s.getMark() - s2.getMark();
            }
        });

edited Jun 03 '14 at 23:12

answered Jun 03 '14 at 23:06

Rod_Algonquin

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You would need to add a secondary comparison: `int compare = s.getMathMark() - s2.getMathMark(); return compare != 0 ? compare : s.getPhysicsMark() - s2.getPhysicsMark();` – shmosel Jun 03 '14 at 23:16
cool ! it works on first block of code ! thanks a lot all of you:) – logcat Jun 03 '14 at 23:58
You could also just use `Collections.max()` instead of `Collections.sort()`. – Kevin Coppock Jun 04 '14 at 00:02
it sort, now if you please tell more about the next part written above? that is; which one will be edited, I will not get that one when search, since for some reason I will have to search the whole ArrayList again and again – logcat Jun 04 '14 at 00:14
if you please look here and suggestme http://stackoverflow.com/questions/24028238/edit-object-arraylist-in-java-again-and-again – logcat Jun 04 '14 at 02:58

How to sort and get highest value from Java Object/ArrayList

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