Why Can Outer Java Classes Access Inner Class Private Members?

Java's Nested Class Access Privileges

Question:

Why can outer Java classes access inner class private members? The following code snippet demonstrates this behavior:

class ABC {
    class XYZ {
        private int x = 10;
    }

    public static void main(String... args) {
        ABC.XYZ xx = new ABC().new XYZ();
        System.out.println("Hello :: " + xx.x); // Why is this allowed?
    }
}

Answer:

Nested classes in Java inherit the privileges of their enclosing class. Specifically, inner classes have access to the outer class's:

• Public and protected members
• Package-private members
• Private members, including those of nested classes

This behavior allows inner classes to encapsulate functionality that is closely tied to the outer class but separates it for readability and maintenance purposes.

Inner classes are essentially members of the outer class, enabling them to access its members, including those marked as private. This access is granted because inner classes:

• Reside in the same file and package as the outer class
• Are tightly coupled with the functionality of the outer class
• Provide a structured way to organize and separate code

Thus, the code snippet above is valid because the inner class XYZ has access to the private member x of the outer class ABC, as they are intimately related and encapsulated together in the same class declaration.

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