Question

I want to sort some objects which are in an ArrayList on the basis of the objects properties.
the object has:

public class Minterm

{
    String minTerm;
    char flagTick;
    String minTermDerive;
    int groupNo;
    String adjGroup;
    static int MaxLiterals;

then i have this in the main method:

ArrayList<Minterm> column =new  ArrayList<Minterm>();

then i add some objects of type Minterm in the list. but at the end i want to organise them and sort them on the member variable groupNo(Ascending order).

i searched and came up with the comparable and comparator interfaces that i tried but didnt succeed. is there any other method to do this? or am i doing the comparator implemnting wrong.

EDIT :
Following is the code i wrote for Comparator. Please confirm if it will sort in ascending?

package backEnd;

import java.util.Comparator;

public class Comp implements Comparator<Minterm>
{
        @Override
        public int compare(Minterm a, Minterm b) 
        {
            return a.getgroupOne().compareTo(b.getgroupOne());
        }
}

i run it as:

Collections.sort(column , new Comp());

seems to be working fine. but i dont have a sound understanding of it.
Please confirm if it will sort in ascending?

Answer 1

You should let Minterm implement Comparable<MinTerm> or write a custom Comparator for MinTerm and then use Collections.sort.

Using a comparator it would look like this:

Collections.sort(column, new Comparator<Minterm>() {
    @Override
    public int compare(Minterm o1, Minterm o2) {
        return Integer.valueOf(o1.groupNo).compareTo(o2.groupNo);
    }
});

Regarding your edit:

Yes. that sorts Minterms based on the groups in ascending order.