Using Comparable for multiple dynamic fields of VO in java

Question

I have a class

public class StudentVO {
   int age;
   String name;  
}

I used the same class in two different areas. At one place i need t

Answer 1

I recently had to solve this problem, too. Not sure if this is exactly the same scenario as yours, but I had to write an in-memory sort for zero or more columns of a grid, handwaving over OOM conditions, etc, because my problem was very limited in scope.

I wrote a comparator for each column and a comparator that took a list of comparators. As I identified which columns needed to be sorted and in what order, I added an instance of the corresponding comparator to the list of comparators. Then, use the chained comparator to execute the actual sort.

public class MyObject
{
    private String name;
    private int age;
    private Date registered;
}

So, something like this for each comparator:

public class NameComparator
    implements Comparator
{
    public int compare(MyObject o1, MyObject o2)
    {
        return o1.getName().compareTo(o2.getName);
    }
}

This for the chained comparator:

public class ChainedComparator
    implements Comparator
{
    public int compare(MyObject o1, MyObject o2) {
        for(Comparator comparator : comparators) {
            int result = comparator.compare(o1,o2);
            if(result != 0) {
                return result;
            }
        }
        return 0;
    }
}
    private List> comparators = new ArrayList<>();
}

Left to your imagination is parsing the sorts and building the chained comparator. I actually made this a bit more complicated because I also incorporated a direction which I implemented by swapping the order of parameters in the call to the sub-comparator in the chained comparator as needed.