Low-level design (LLD) for a translation service:

Language detection: The service will need to be able to identify the language of the input text. This might involve using natural language processing (NLP) techniques such as language modeling or machine learning algorithms to classify the language.
Translation engine: The service will need to translate the input text from one language to another. This might involve using machine translation algorithms or integrating with a third-party translation API.
User accounts and authentication: The service will need to allow users to create accounts, log in, and log out. We will also need to implement measures to ensure the security of user accounts, such as password hashing and potentially two-factor authentication.
User interface: The service will need to provide a user interface for users to input the text to be translated and select the desired language. This will likely involve creating forms and handling the associated server-side logic to process the input and return the translated text.
Caching: To improve performance, the service might implement caching of previously translated text to avoid having to translate the same text multiple times.
Monitoring and logging: The service will need to monitor its performance and collect logs for debugging and analysis. This might involve implementing monitoring tools such as metrics and logging libraries to track the service's performance and identify any issues.

Code

import java.util.*;

// Strategy Pattern for Translation Algorithms
interface TranslationAlgorithm {
    String translate(String text, Language sourceLanguage, Language targetLanguage);
}

class DictionaryBasedTranslation implements TranslationAlgorithm {
    private Dictionary dictionary;

    public DictionaryBasedTranslation(Dictionary dictionary) {
        this.dictionary = dictionary;
    }

    @Override
    public String translate(String text, Language sourceLanguage, Language targetLanguage) {
        return dictionary.getTranslation(text, sourceLanguage, targetLanguage);
    }
}

class MemoryBasedTranslation implements TranslationAlgorithm {
    private TranslationMemory translationMemory;

    public MemoryBasedTranslation(TranslationMemory translationMemory) {
        this.translationMemory = translationMemory;
    }

    @Override
    public String translate(String text, Language sourceLanguage, Language targetLanguage) {
        return translationMemory.getTranslation(text, sourceLanguage, targetLanguage);
    }
}

// Main Translation Service
public class TranslationService {
    private LanguageDetector languageDetector;
    private TranslationEngine translationEngine;
    private Dictionary dictionary;
    private UserInterface userInterface;
    private TranslationMemory translationMemory;
    private QualityAssurance qualityAssurance;

    public TranslationService() {
        this.languageDetector = new LanguageDetector();
        this.dictionary = new Dictionary();
        this.translationMemory = new TranslationMemory();
        this.translationEngine = new TranslationEngine();
        this.qualityAssurance = new QualityAssurance();
        this.userInterface = new UserInterface();

        // Set initial translation strategies
        translationEngine.addTranslationAlgorithm(new DictionaryBasedTranslation(dictionary));
        translationEngine.addTranslationAlgorithm(new MemoryBasedTranslation(translationMemory));
    }

    public void translate(String text, Language targetLanguage) {
        Language sourceLanguage = languageDetector.detectLanguage(text);
        String translatedText = translationEngine.translate(text, sourceLanguage, targetLanguage);
        translationMemory.addTranslation(text, translatedText, sourceLanguage, targetLanguage);
        String feedback = qualityAssurance.checkQuality(text, translatedText, sourceLanguage, targetLanguage);
        translationEngine.improve(feedback);
        userInterface.displayTranslation(translatedText);
    }
}

// Observer Pattern for notifying on translation completion
interface TranslationObserver {
    void notifyTranslation(String translatedText);
}

class UserNotificationService implements TranslationObserver {
    @Override
    public void notifyTranslation(String translatedText) {
        System.out.println("Notification: Your translation is ready: " + translatedText);
    }
}

class UserInterface {
    private List<TranslationObserver> observers;

    public UserInterface() {
        this.observers = new ArrayList<>();
    }

    public void addObserver(TranslationObserver observer) {
        observers.add(observer);
    }

    public void displayTranslation(String translatedText) {
        System.out.println("Translation: " + translatedText);
        notifyObservers(translatedText);
    }

    private void notifyObservers(String translatedText) {
        for (TranslationObserver observer : observers) {
            observer.notifyTranslation(translatedText);
        }
    }
}

// Translation Engine with support for multiple translation algorithms (Strategy Pattern)
public class TranslationEngine {
    private List<TranslationAlgorithm> translationAlgorithms;

    public TranslationEngine() {
        this.translationAlgorithms = new ArrayList<>();
    }

    public void addTranslationAlgorithm(TranslationAlgorithm algorithm) {
        translationAlgorithms.add(algorithm);
    }

    public String translate(String text, Language sourceLanguage, Language targetLanguage) {
        for (TranslationAlgorithm algorithm : translationAlgorithms) {
            String result = algorithm.translate(text, sourceLanguage, targetLanguage);
            if (result != null && !result.isEmpty()) {
                return result;
            }
        }
        return "Translation not found";
    }

    public void improve(String feedback) {
        // Use feedback to improve translation algorithms
        System.out.println("Improving translation based on feedback: " + feedback);
    }
}

// Language Detector using basic language detection (can be enhanced with NLP)
public class LanguageDetector {
    public Language detectLanguage(String text) {
        // Simulating language detection
        return text.contains("hola") ? Language.SPANISH : Language.ENGLISH;
    }
}

// Quality Assurance to check translation quality
public class QualityAssurance {
    public String checkQuality(String text, String translatedText, Language sourceLanguage, Language targetLanguage) {
        // Check translation quality (dummy implementation for now)
        if (translatedText.length() < text.length()) {
            return "Improve accuracy";
        }
        return "Translation OK";
    }
}

// Translation Memory for caching previously translated texts
public class TranslationMemory {
    private Map<String, Map<LanguagePair, String>> translations;

    public TranslationMemory() {
        this.translations = new HashMap<>();
    }

    public void addTranslation(String text, String translatedText, Language sourceLanguage, Language targetLanguage) {
        LanguagePair languagePair = new LanguagePair(sourceLanguage, targetLanguage);
        translations.computeIfAbsent(text, k -> new HashMap<>()).put(languagePair, translatedText);
    }

    public String getTranslation(String text, Language sourceLanguage, Language targetLanguage) {
        Map<LanguagePair, String> languageMap = translations.get(text);
        if (languageMap != null) {
            return languageMap.get(new LanguagePair(sourceLanguage, targetLanguage));
        }
        return null;
    }
}

// Dictionary for word-level translation lookups
public class Dictionary {
    private Map<String, Map<Language, String>> entries;

    public Dictionary() {
        this.entries = new HashMap<>();
    }

    public String getTranslation(String word, Language sourceLanguage, Language targetLanguage) {
        if (entries.containsKey(word)) {
            return entries.get(word).get(targetLanguage);
        }
        return "No translation found";
    }
}

// Language Enum representing supported languages
public enum Language {
    ENGLISH, SPANISH, FRENCH, GERMAN
}

// LanguagePair to identify a source and target language combination
public class LanguagePair {
    private Language sourceLanguage;
    private Language targetLanguage;

    public LanguagePair(Language sourceLanguage, Language targetLanguage) {
        this.sourceLanguage = sourceLanguage;
        this.targetLanguage = targetLanguage;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        LanguagePair that = (LanguagePair) o;
        return sourceLanguage == that.sourceLanguage && targetLanguage == that.targetLanguage;
    }

    @Override
    public int hashCode() {
        return Objects.hash(sourceLanguage, targetLanguage);
    }
}

// Example usage
public class Main {
    public static void main(String[] args) {
        TranslationService translationService = new TranslationService();
        UserNotificationService notificationService = new UserNotificationService();
        translationService.userInterface.addObserver(notificationService);

        translationService.translate("hello", Language.SPANISH);
    }
}

Design (LLD) Translation service - Machine Coding

Table of contents