Understanding Inheritance and Polymorphism

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Hi, I've been delving further into Java programming recently, and I've come across a notion that may use some clarification: inheritance and polymorphism. I wrote a bit of code that I feel supports these notions, but I'm having some problems. Here is the code snippet:

Java:
// Parent class
class Animal {
    void sound() {
        System.out.println("Animal makes a sound");
    }
}

// Child class inheriting from Animal
class Dog extends Animal {
    void sound() {
        System.out.println("Dog barks");
    }
}

// Main class to demonstrate polymorphism
public class Main {
    public static void main(String[] args) {
        Animal myAnimal = new Dog(); // Polymorphism
        myAnimal.sound(); // Output: "Dog barks"
    }
}

However, I'm having a couple issues with this code.

Inheritance Issue: Although Dog inherits from Animal, I'm not sure whether I'm using inheritance appropriately in this case. Could you please explain how inheritance works in Java and whether there are any concerns with the inheritance link between Animal and Dog?

Polymorphism Problem: While I'm attempting to illustrate polymorphism by assigning a Dog object to an Animal reference, I'm not sure whether I'm actually accomplishing polymorphic behavior. Could you explain how polymorphism should be performed appropriately in Java?

Output Mismatch: Despite anticipating the output "Dog barks," I do not obtain the anticipated outcome when I execute the application. Is there something lacking in the code that is causing the outcome to differ from what I expected?

Code Structure Clarification: While I've arranged the code to demonstrate inheritance and polymorphism as shown here, I'm not sure if there are any adjustments or revisions I should do to increase its clarity and functionality. Are there any recommendations for reorganizing the code to properly show these concepts?

I would highly appreciate your aid in resolving these challenges and offering advise on how to improve my grasp of inheritance and polymorphism in Java.
 
Joined
Jan 24, 2024
Messages
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Hi, I've been delving further into Java programming recently, and I've come across a notion that may use some clarification: inheritance and polymorphism. I wrote a bit of code that I feel supports these notions, but I'm having some problems. Here is the code snippet:

Java:
// Parent class
class Animal {
    void sound() {
        System.out.println("Animal makes a sound");
    }
}

// Child class inheriting from Animal
class Dog extends Animal {
    void sound() {
        System.out.println("Dog barks");
    }
}

// Main class to demonstrate polymorphism
public class Main {
    public static void main(String[] args) {
        Animal myAnimal = new Dog(); // Polymorphism
        myAnimal.sound(); // Output: "Dog barks"
    }
}

However, I'm having a couple issues with this code.

Inheritance Issue: Although Dog inherits from Animal, I'm not sure whether I'm using inheritance appropriately in this case. Could you please explain how inheritance works in Java and whether there are any concerns with the inheritance link between Animal and Dog?

Polymorphism Problem: While I'm attempting to illustrate polymorphism by assigning a Dog object to an Animal reference, I'm not sure whether I'm actually accomplishing polymorphic behavior. Could you explain how polymorphism should be performed appropriately in Java?

Output Mismatch: Despite anticipating the output "Dog barks," I do not obtain the anticipated outcome when I execute the application. Is there something lacking in the code that is causing the outcome to differ from what I expected?

Code Structure Clarification: While I've arranged the code to demonstrate inheritance and polymorphism as shown here, I'm not sure if there are any adjustments or revisions I should do to increase its clarity and functionality. Are there any recommendations for reorganizing the code to properly show these concepts?

I would highly appreciate your aid in resolving these challenges and offering advise on how to improve my grasp of inheritance and polymorphism in Java.
  1. Inheritance Issue: Your usage of inheritance is correct. The Dog class correctly extends the Animal class. This means that Dog inherits the properties and methods of the Animal class. Inheritance allows you to create a general class (Animal in this case) and then extend it to more specialized classes (Dog). Your code structure for inheritance is appropriate.
  2. Polymorphism Problem: Polymorphism is achieved in your code when you declare an Animal reference (myAnimal) and assign it a Dog object. This is known as upcasting. The overridden method sound() in the Dog class is invoked at runtime because Java determines the actual type of the object at runtime. Your use of polymorphism is correct.
  3. Output Mismatch: The output mismatch is likely due to the method being overridden in the Dog class. When you have a method in the subclass (Dog) with the same signature as the method in the superclass (Animal), the subclass method will override the superclass method. In your case, the sound() method in Dog is overriding the sound() method in Animal. Therefore, the output will be "Dog barks," as expected.
    If you are not getting the expected output, please ensure that your code is compiled and executed correctly. If there's still an issue, it might be due to external factors not present in the provided code snippet.
  4. Code Structure Clarification: Your code structure is fine for illustrating inheritance and polymorphism. However, you might consider adding the @Override annotation above the sound() method in the Dog class. This annotation is not mandatory, but it helps the compiler catch errors if the method in the child class doesn't actually override a method in the parent class.
    Here's an updated version of your Dog class:

    Java:
    class Dog extends Animal {
    @Override
    void sound() {
    System.out.println("Dog barks");
    }
    }


    This can help in maintaining and understanding the code, especially in larger projects.
In summary, your code demonstrates the concepts of inheritance and polymorphism correctly. If you encounter any issues with the output, please double-check your code execution environment. If you have any specific error messages or unexpected behaviors, feel free to provide more details.
 

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