工厂模式的演变

最简单的工厂模式

    public static SortStrategy getSortingStrategy(String strategyName) {
        return switch (strategyName) {
            case "bubble" -> new BubbleSort();
            case "selection" -> new SelectionSort();
            case "merge" -> new MergeSort();
            case "quick" -> new QuickSort();
            default -> new ShellSort();
        };
    }

基于HashMap的工厂模式

class SortFactory {
    static Map<String, SortStrategy> strategyMap = new HashMap<>();

    // initialize the strategy instances.
    static {
        strategyMap.put("quicksort", new QuickSort());
        strategyMap.put("mergesort", new MergeSort());
        strategyMap.put("heapsort", new HeapSort());        
    }

    public static SortStrategy getSortStrategy(String sortType) {
        // Return strategy from map, default to BubbleSort.
        return strategyMap.getOrDefault(sortType, new BubbleSort());
    }
}

基于反射的工厂模式

    static {
        Properties props = new Properties();
        try (InputStream input = SortFactory.class.getClassLoader().getResourceAsStream(CONFIG_FILE)) {
            props.load(input);
            for (String sortName : props.stringPropertyNames()) {
                String className = props.getProperty(sortName);
                Class<?> clazz = Class.forName(className); // Load class dynamically
                SortStrategy strategy = (SortStrategy) clazz.getDeclaredConstructor().newInstance(); // Instantiate
                strategyMap.put(sortName.toLowerCase(), strategy);
            }
        } catch (Exception e) {
            // No error handling for simplicity
        }
        strategyMap.putIfAbsent("bubblesort", DEFAULT_STRATEGY); // Ensure default
    }