Packages and Interfaces: Modularity & Contract Design

/**
 * DevAscent Academy — Unit 8 Capstone Project
 * Demonstrates Packages, Interfaces, Multiple Inheritance, and Default Methods.
 */

// 1. Interface 1: Transmission Protocol
interface Transmittable {
    // Implicitly public static final
    String DEFAULT_PROTOCOL = "TLS_1.3";

    void transmit(String destination);

    // Default method with fallback behavior
    default void verifyHandshake() {
        System.out.println("  [Transmittable] Standard handshake verified on " + DEFAULT_PROTOCOL);
    }
}

// 2. Interface 2: Cryptographic Contract
interface Encryptable {
    String encryptPayload(String rawText);

    // Colliding default method with same signature as Transmittable!
    default void verifyHandshake() {
        System.out.println("  [Encryptable] Zero-knowledge cryptographic handshake verified.");
    }

    // Static utility method inside interface (Java 8+)
    static boolean isKeyLengthSecure(int bits) {
        return bits >= 256;
    }
}

// 3. Concrete Service: Multiple Interface Implementation
class SecureMessagePayload implements Transmittable, Encryptable {
    private final String messageId;
    private String content;

    public SecureMessagePayload(String messageId, String content) {
        this.messageId = messageId;
        this.content = content;
    }

    @Override
    public void transmit(String destination) {
        System.out.printf("Transmitting Packet [%s] to '%s' | Payload: %s%n", 
                this.messageId, destination, this.content);
    }

    @Override
    public String encryptPayload(String rawText) {
        // High-speed simple Caesar hash simulation for demo
        StringBuilder cipher = new StringBuilder();
        for (char c : rawText.toCharArray()) {
            cipher.append((char)(c + 3));
        }
        this.content = cipher.toString();
        return this.content;
    }

    // Disambiguating colliding default methods from Transmittable & Encryptable!
    @Override
    public void verifyHandshake() {
        System.out.println("--- Resolving Diamond Default Method Collision ---");
        Transmittable.super.verifyHandshake(); // Explicit delegation
        Encryptable.super.verifyHandshake();   // Explicit delegation
    }
}

// 4. Execution Driver
public class SecureMessagingPipeline {
    public static void main(String[] args) {
        System.out.println("==================================================");
        System.out.println("  DEVASCENT ENTERPRISE SECURE MESSAGING PIPELINE  ");
        System.out.println("==================================================");

        // Static Interface Method verification
        boolean secure = Encryptable.isKeyLengthSecure(256);
        System.out.println("Static Interface Check (AES-256): " + (secure ? "COMPLIANT" : "WEAK"));

        SecureMessagePayload packet = new SecureMessagePayload("MSG-9041", "TRANSFER_FUNDS $50,000");

        // Invoking overridden diamond default method
        packet.verifyHandshake();

        // Encrypt and Transmit
        System.out.println("--------------------------------------------------");
        packet.encryptPayload("TRANSFER_FUNDS $50,000");
        packet.transmit("https://api.devascentacademy.me/vault");
        System.out.println("==================================================");
    }
}