Why Doesn't Java Allow `super.super.method()`?

Why Java Restricts Access to Super.super.method()

In Java, the syntax super.super.method(); is not allowed, despite being present in many other languages. This restriction stems from Java's emphasis on encapsulation, ensuring that subclasses cannot violate the behavior of their parent classes.

Encapsulation forces subclasses to adhere to the rules defined by their superclasses. Suppose we have a class hierarchy with a parent class (Items) and two subclasses (RedItems and BigRedItems). RedItems enforces that all items it contains must be red, while BigRedItems further restricts them to being large and red.

In this scenario, allowing super.super.add(); would break encapsulation. A subclass (NaughtyItems) could bypass RedItems's red item constraint by directly calling super.super.add();:

public class NaughtyItems extends RedItems {
    @Override
    public void add(Item item) {
        // I don't care if it's red or not. Take that, RedItems!
        super.super.add(item);
    }
}

This would violate the invariant in RedItems, allowing items of any color to be added to NaughtyItems.

Essentially, super.super.method(); allows subclasses to bypass the behavior of multiple parent classes, undermining the encapsulation principles of inheritance. Java prohibits this to ensure subclasses respect their parent classes' behavior and maintain well-structured class hierarchies.

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