java - How to reduce code by using a superclass?

Question

I would like to refactor some code that currently consists of a superclass and two subclasses.

These are my classes:

public class Animal {
    int a;
    int b;
    int c;
}

public class Dog extends Animal {
    int d;
    int e;
}

public class Cat extends Animal {
    int f; 
    int g;
}

This is my current code:

ArrayList<Animal> listAnimal = new ArrayList<>();

if (condition) {
    Dog dog = new Dog();
    dog.setA(..);
    dog.setB(..);
    dog.setC(..);
    dog.setD(..);
    dog.setE(..);   
    listAnimal.add(dog);

} else {
    Cat cat = new Cat();
    cat.setA(..);
    cat.setB(..);
    cat.setC(..);
    cat.setF(..);
    cat.setG(..);
    listAnimal.add(cat);
}

How can I refactor the code regarding the common attributes?

I would like something like that:

Animal animal = new Animal();
animal.setA(..);
animal.setB(..);
animal.setC(..);

if (condition) {
    Dog anim = (Dog) animal; //I know it doesn't work
    anim.setD(..);
    anim.setE(..);  
} else {
    Cat anim = (Cat) animal; //I know it doesn't work
    anim.setF(..);
    anim.setG(..);
}

listAnimal.add(anim);

question from:https://stackoverflow.com/questions/52513557/how-to-reduce-code-by-using-a-superclass

Answer 1

Your idea to have a variable of type Animal is good. But you also have to make sure to use the right constructor:

Animal animal; // define a variable for whatever animal we will create

if (condition) {
    Dog dog = new Dog(); // create a new Dog using the Dog constructor
    dog.setD(..);
    dog.setE(..);  
    animal = dog; // let both variables, animal and dog point to the new dog
} else {
    Cat cat = new Cat(); 
    cat.setF(..);
    cat.setG(..);
    animal = cat;
}

animal.setA(..); // modify either cat or dog using the animal methods
animal.setB(..);
animal.setC(..);

listAnimal.add(animal);

Hint: If an Animal is always either Cat or Dog consider making Animal abstract. Then the compiler will automatically complain whenever you try to do new Animal().