


How Can I Achieve Limited Access to Private Methods in Java Without Using the 'Friend' Concept?
Providing Limited Access to Private Methods in Java
In Java, it's not directly possible to replicate the C "friend" concept, which allows access to private members of a class to external entities. However, a similar behavior can be achieved using alternative techniques.
The Love Signature Approach
One clever approach to achieve controlled access is by using a "secret" signature. Here's how it works:
- Create a public class in one package that represents the "secret signature" required for accessing the private methods in another package. This signature class can contain a private constructor to ensure exclusivity.
- In the class needing access to the private members, define public methods that accept instances of the signature class as parameters.
- When calling the public methods from the other package, the signature class instance acts as a "proof" to allow the invocation.
Example:
Consider two classes, Romeo and Juliet, from different packages. Romeo needs to access private methods in Juliet without making it a subclass.
Juliet's Code:
// Capulet package public class Juliet { public static void cuddle(Romeo.Love love) { Objects.requireNonNull(love); // Juliet's private methods can be accessed here. } }
Romeo.Love is a public class with a private constructor, ensuring only Romeo can create an instance.
Romeo's Code:
// Montague package public class Romeo { public static final class Love { private Love() {} } private static final Love love = new Love(); public static void cuddleJuliet() { Juliet.cuddle(love); } }
This approach leverages the exclusivity of the signature class constructor to grant selective access to the desired methods while maintaining encapsulation and privacy.
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