How Can You Check If a Method Is Overridden in a Java Class?

What is the process for checking if a method has been overridden in a Java class?

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

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

In Java, determining if a method has been overridden in a subclass can be essential for understanding class behavior and achieving polymorphism. An overridden method provides a new implementation in a subclass, while the original remains in the parent class. We can use various approaches to check for method overriding, such as reflection, and carefully analyzing the class hierarchy.

import java.lang.reflect.Method;

public class MethodOverrideChecker {
    public static void main(String[] args) throws NoSuchMethodException {
        Class<?> parentClass = Parent.class;
        Class<?> childClass = Child.class;

        // Check if 'display' method in Child overrides Parent's display method
        Method parentMethod = parentClass.getMethod("display");
        Method childMethod = childClass.getMethod("display");

        // Check if the method in Child is overridden
        if (childMethod.getDeclaringClass() != parentClass) {
            System.out.println("display() method is overridden in Child class.");
        } else {
            System.out.println("display() method is NOT overridden in Child class.");
        }
    }
}

Causes

• Using the `@Override` annotation incorrectly or forgetting to use it altogether can cause confusion about whether a method has been properly overridden.
• Misunderstanding the inheritance hierarchy may lead to incorrect assumptions about method implementations.

Solutions

• Utilize Java's reflection API to check method declarations.
• Review the class definition and its superclasses to confirm overridden methods.
• Always use the `@Override` annotation when overriding to improve code clarity.

Mistake: Not using the `@Override` annotation, leading to confusion over method implementations.

Solution: Always apply the `@Override` annotation to methods that are intended to override superclass methods.

Mistake: Assuming all methods declared in a subclass override their superclass counterparts.

Solution: Verify method declarations and the parent class to ensure that intended method overriding is present.