How Can I Access Subclass Methods from a Superclass in Java?

Calling Subclass Methods from Superclass

Problem

In Java, when inheriting classes and creating subclasses, it's common to encounter issues accessing subclass-specific methods from within the superclass. This occurs when you instantiate a subclass object and assign it to a superclass variable.

Solution

To resolve this limitation, you can use either of the following methods:

• Declare the variable as the derived class:

Cat cat = new Cat("Feline", 12, "Orange");
cat.getName(); // OK
cat.getColor(); // OK (getColor() is in Cat)

• Cast the variable to the desired concrete type:

Pet pet = new Cat("Feline", 12, "Orange");
((Cat)pet).getName(); // OK
((Cat)pet).getColor(); // OK (explicitly treated as Cat)

When you perform a cast, you temporarily treat the object as an instance of the specified type. This allows you to access subclass-specific members and methods.

Example

Consider the following modified Main class:

public class Kennel {
    public static void main(String[] args) {
        // Create the pet objects
        Cat cat = new Cat("Feline", 12, "Orange");
        Pet dog = new Dog("Spot", 14, "Dalmatian");
        Pet bird = new Bird("Feathers", 56, 12);

        // Print out the status of the animals
        System.out.println("I have a cat named " + cat.getName()
                + ". He is " + cat.getAge() + " years old."
                + " He is " + cat.getColor()
                + ". When he speaks he says " + cat.speak());

        // Using a cast to access a subclass-specific method
        ((Cat)dog).getBreed(); // dog is treated as Cat to access getBreed()
        System.out.println("I also have a dog named " + dog.getName()
                + ". He is " + dog.getAge() + " years old."
                + " He is a " + ((Cat)dog).getBreed()
                + ". When he speaks he says " + dog.speak());

        System.out.println("And Finally I have a bird named "
                + bird.getName() + ". He is " + bird.getAge() + " years old."
                + " He has a wingspan of " + bird.getWingspan() + " inches."
                + " When he speaks he says " + bird.speak());
    }
}

In this example, the Main class successfully retrieves the breed of the dog using a cast.

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