Question

I need the following functionality

Given two sorted lists, merge them

I have this skeleton Java code:

public class MergeLists{
   public List merge(List l1, List l2){
      List l3;
      // merge l1, l2 in to l3
      return l3;
   }

   public static void main(){
      // populate list1 and list2
      MergeLists ml = new MergeLists();
      List l3 = ml.merge(l1,l2);
   }
}

Is this single method class the right approach? I feel like the almost-empty class is staring at me to say that this is bad design. I initially had List L3 as private member of MergeLists but then I thought, merge(l1,l2) can be called multiple times with the same object, which required l3 to be local to merge(l1,l2).
I read that using static method is even worse for code re-usability. Please advise. Thank you.

Answer 1

In this case, since you have no true member data, making the single method a static method inside the class would be the appropriate design choice:

public class ListUtils
{
    public static List Merge(List l1, Listl2)
    {
        List l3 = new List();
        // merge l1 and l3 into l3
        return l3;
    }
}

You can then use the code without having to create an instance of your class (especially when it serves no purpose):

List l1 = new List();
List l2 = new List();
// Fill the lists

List merged = ListUtils.Merge(l1, l2);