[FIXED] How to create generic code for objects of different types

Issue

I have an entity that has as children several lists of objects that, although they have different classes, all have the order attribute, in several parts I end up with repeated code, for example in one part I need to order the lists by that attribute and I cannot simplify because they are of different type.

The relevant part of the entity is this:

contenido={
  "educaciones":[
    {
      ...
      "orden":0
    },{
      ...
      "orden":1
    }
  ],
  "experiencias":[
    {
      ...
      "orden":0
    },{
      ...
      "orden":1
    }
  ]
},
...

The code I would like to simplify:

if(tipo.equals("experiencias")){
   List<Experiencia> iterable=contenido.getExperiencias();
   for(int i = 0; i < iterable.size(); i++){
      iterable.get(i).setOrden( orden.get(i) ); //orden = [0,3,5,...]
   }
   iterable.sort((it1,it2)-> it1.getOrden().compareTo(it2.getOrden()));
}else if(tipo.equals("educaciones")){
   List<Educacion> iterable=contenido.getEducaciones();
   for(int i = 0; i < iterable.size(); i++){
      iterable.get(i).setOrden( orden.get(i) );
   }
   iterable.sort((it1,it2)-> it1.getOrden().compareTo(it2.getOrden()));
}else if...

Is there a way to create a code that is more generic and supports different objects?

Solution

Create an interface for the methods that are common between all you classes:

interface HasOrden {
  int getOrden();
  void setOrden(int i);
}

Each of your classes needs to implement HasOrden.

Then you can declare sortOrden function:

import java.util.ArrayList;
import java.util.List;

interface HasOrden {
    int getOrden();
    void setOrden(int i);
}
class Experiencia implements HasOrden {
    private final String name;
    int orden;

    public Experiencia(String name) {
        this.name = name;
    }

    @Override
    public int getOrden() {
        return orden;
    }

    @Override
    public void setOrden(int i) {
        orden = i;
    }

    public String toString() {
        return name;
    }
}
public class Eg {
    static void sortOrden(List<? extends HasOrden> l, List<Integer> order) {
        if (l.size() != order.size()) {
            throw new RuntimeException("length mismatch");
        }
        for (int i = 0; i < l.size(); i++) {
            l.get(i).setOrden(order.get(i));
        }
        l.sort((it1,it2)-> Integer.compare(it1.getOrden(), it2.getOrden()));
    }
    public static void main(String[] args) {
        List<Experiencia> items = new ArrayList<>(List.of(new Experiencia("a"), new Experiencia("b")));
        List<Integer> order = List.of(2,1);
        sortOrden(items, order);
        System.out.println(items);
    }
}

You can call sortOrden on any list of HasOrden instances.

Answered By - tgdavies
Answer Checked By - Marilyn (JavaFixing Volunteer)