如何为不同类型的对象创建通用代码

Question

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?

Answer 1

you can try to create a List<?> - list with a dynamic type outside of your if else block and move your duplicated code outside too and at the end of the if else block. In addition, you have to create a common class or some interface for your classes, which holds all the common field you needed

public class Main {

public static class Something {
    private Integer sth;
    public Integer getSth() {
        return sth;
    }
    public void setSth(Integer sth) {
        this.sth = sth;
    }
}
public static class ThisClass extends Something {
    private Integer num;
    public ThisClass(Integer num) {
        this.num = num;
    }
    public Integer getNum() {
        return num;
    }
    public void setNum(Integer num) {
        this.num = num;
    }
}
public static class ThatClass extends Something {
    private String str;
    public ThatClass(String str) {
        this.str = str;
    }
    public String getStr() {
        return str;
    }
    public void setNum(String str) {
        this.str = str;
    }
    
}

public static List<? extends Something> sortList(Class<?> itemClass, List<? extends Something> list) 
throws Exception {
    for(int i = 0; i < list.size(); i++){
        list.get(i).setSth(i);
    }
    list.sort((it1,it2)-> it1.getSth().compareTo(it2.getSth()));
    return list;
}

public static void main(String[] args) {
    System.out.println("Hello World");
    List<? extends Something> someList = new ArrayList<>();
    boolean check = true;
    if(check) {
        someList = Arrays.asList(new ThisClass(1),new ThisClass(1),new ThisClass(1),new ThisClass(1));
    } else {
        someList = Arrays.asList(new ThatClass("a"), new ThatClass("a"),new ThatClass("a"),new ThatClass("a"));
    }
    try {
        someList = sortList(ThisClass.class, someList);
        for(int i = 0; i < someList.size(); i++){
            System.out.println(someList.get(i).getSth());
        }   
    } catch (Exception e) {
        e.printStackTrace();
    }
    
}

}

Answer 2

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.