CODEWITHSUNDEEP
javasortingarraylistcollections
Stack
Stack

Reputation: 111

How to sort with 2 Objects from 2 Classes by 1 properties

Assume I have two classes:

class 1:

class Person{
    String name;
    int age;
    public Person(){}
    public Person(String name, int age){
        this.name = name;
        this.age = age;
    }
    @Override
    String toString(){
        return "Name: "+name + "\tAge: "+age;
    }
}

class 2

class Animal{
    String name;
    int age;
    public Animal(){}
    public Animal(String name, int age){
        this.name = name;
        this.age = age;
    }
    @Override
    String toString(){
        return "Name: "+name + "\tAge: "+age;
    }
}

And I create a List Object to stored 2 classes Person and Animal

List newList = new ArrayList<>();
newList.add( new Person("person", 20);
newList.add( new Person("aPerson",20);
newList.add( new Animal("animal",20);
newList.add( new Animal("aAnimal",20);

Now i want sort newList by name but i don't know how to do it. With one Class I can Create Class SortByName and compare name between two Object, But with two Class i can not

Upvotes: 0

Views: 380

Answers (3)

Vikas
Vikas

Reputation: 7165

After creating a Base class/interface as suggested in other answers, you can sort as with Comparator.comparing,

newList.sort(Comparator.comparing(Entity::getName));

Upvotes: 1

CodeMatrix
CodeMatrix

Reputation: 2154

An abstraction for that specific case is needed that holds all the information which both entities need. E. g. an interface called Entity which has the method getName().

Example:

public interface Entity {
    String getName();
}

public class Person implements Entity {

...
    @Override
    public String getName() {
        return name;
    }
}

public class Animal implements Entity {

...
    @Override
    public String getName() {
        return name;
    }
}

After you got this you can use it by type:

List<Entity> entities = new ArrayList<>();
entities.add(new Person("person", 20);
entities.add(new Person("aPerson", 20);
entities.add(new Animal("animal", 20);
entities.add(new Animal("aAnimal", 20);
entities.sort((o1, o2) -> o1.getName().compareTo(o2.getName());

It would also be possible to use an abstract class.

Upvotes: 1

Pbd
Pbd

Reputation: 1319

What you need is an Interface. Both your Animal and Person class offer name as one of their properties, so you can have an Interface say Nameable in this regard to essentially specify that your class definitely has name property.

You'll code to the Nameable interface so as to create a list of Nameable's and you can create a sorter on that list.

List<Nameable> list = new ArrayList<>();
newList.add( new Person("person", 20);
newList.add( new Person("aPerson",20);
newList.add( new Animal("animal",20);
newList.add( new Animal("aAnimal",20);

list.sort(new Comparator<Nameable>() {
    public int compare(Nameable o1, Nameable o2) {
        return o1.getName().compareTo(o2.getName());
    }
});

The interface ans its usage:

Nameable.java

public interface Nameable {
    String getName();
}

public class Person implements Nameable {
   ...

   String getName() {
      return name;
   }

   ...
}

public class Animal implements Nameable {
   ...

   String getName() {
      return name;
   }

   ...
}

Upvotes: 2

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