Say I have 2 arrays of objects which all extend the same abstract class, and I want the second list's first element to be a new instance of the same class which the first element in the first array is (this assumes that they take the same parameters).
Animals[] animals1 = new Animals[] {new Cat(), new Dog()...}
Animals[] animals2 = new Animals[] {new animals1[0].getClass()} //doesn't work obviously
Is there a way of doing this?
You could do something like this:
Animal.java
public interface Animal {
}
Cat.java:
public class Cat implements Animal {
}
Dog.java:
public class Dog implements Animal {
}
Code to do the mapping:
Animal[] animals1 = new Animal[] {new Cat(), new Dog()};
Animal[] animals2 = Arrays.stream(animals1).map(a -> {
Animal animal = null;
try {
animal = a.getClass().getDeclaredConstructor().newInstance();
} catch (Exception e) {
e.printStackTrace();
}
return animal;
}).toArray(Animal[]::new);
I would create an abstract method newInstance() in the abstract base class, and make the subclasses create and return its own kind. For instance,
public abstract class Animal {
// ... other methods
public abstract Animal newInstance(/* parameters */);
}
public class Dog extends Animal {
// ... other methods, fields
@Override
public Animal newInstance(/* parameters */) {
Dog d = new Dog(/* ... */);
// ...
return d;
}
}
// do this for other animals, they should instantiate and return their class
and for the list:
Animals[] animals2 = new Animals[] {animals[0].newInstance(/* ... */), ...};
