How to Override a Method in a Java Object Instance

How can I override a method in an instantiated Java object?

class Parent {
    void display() {
        System.out.println("Parent Display");
    }
}

class Child extends Parent {
    @Override
    void display() {
        System.out.println("Child Display");
    }
}

public class Main {
    public static void main(String[] args) {
        Parent obj = new Child();
        obj.display(); // This will call the overridden method in Child
    }
}

In Java, method overriding allows a subclass to provide a specific implementation of a method that is already defined in its superclass. To override a method, the subclass must have the same method signature as the superclass method. This fundamental feature enables polymorphism in Java, allowing for dynamic method resolution at runtime.

class Animal {
    void sound() {
        System.out.println("Animal makes sound");
    }
}

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

public class Main {
    public static void main(String[] args) {
        Animal myDog = new Dog();
        myDog.sound(); // Calls Dog's sound method
    }
}

Causes

• The method must be declared in the superclass.
• The subclass must use the @Override annotation for clarity and to prevent errors.
• The method signature (name and parameters) in the subclass must match the one in the superclass.

Solutions

• Define a superclass method that you intend to override.
• Create a subclass that extends the superclass.
• Use the same method name and parameters in the subclass method to implement the new functionality.
• Use the @Override annotation in the subclass method to indicate that you are overriding a method from the superclass.

Mistake: Not using the @Override annotation for the method in the subclass.

Solution: Always include the @Override annotation to help catch errors during compilation and improve code readability.

Mistake: Changing the method signature in the subclass.

Solution: Ensure that the method name and parameter types match exactly with the superclass method.

Mistake: Attempting to override a static method.

Solution: Remember that static methods cannot be overridden in the same way as instance methods; instead, they are hidden.