public class CacheRefreshThread extends Thread {
    private CacheManager cacheManager;
    
    public CacheRefreshThread(CacheManager cacheManager) {
        this.cacheManager = cacheManager;
    }
    
    @Override
    public void run() {
        while (true) {
            try {
                // 每30秒刷新一次緩存
                Thread.sleep(30000);
                cacheManager.refresh();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                break;
            }
        }
    }
}

// 使用方式
CacheManager productCache = new ProductCacheManager();
new CacheRefreshThread(productCache).start();

public class CacheRefreshTask implements Runnable {
    private CacheManager cacheManager;
    
    public CacheRefreshTask(CacheManager cacheManager) {
        this.cacheManager = cacheManager;
    }
    
    @Override
    public void run() {
        while (!Thread.currentThread().isInterrupted()) {
            try {
                // 每30秒刷新一次緩存
                Thread.sleep(30000);
                cacheManager.refresh();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                break;
            }
        }
    }
}

// 使用方式
CacheManager productCache = new ProductCacheManager();
// 創(chuàng)建核心線程池統(tǒng)一管理
ExecutorService executor = Executors.newFixedThreadPool(5);
executor.submit(new CacheRefreshTask(productCache));

// 應(yīng)用關(guān)閉時(shí)優(yōu)雅 shutdown
Runtime.getRuntime().addShutdownHook(new Thread(executor::shutdownNow));

public class OrderProcessor {
    // 父類定義的訂單處理流程
    public final void process(Order order) {
        // 1. 參數(shù)校驗(yàn)
        validateParams(order);
        // 2. 庫(kù)存校驗(yàn)
        validateStock(order);
        // 3. 扣減庫(kù)存
        deductStock(order);
        // 4. 創(chuàng)建訂單
        createOrder(order);
    }
    
    protected void validateParams(Order order) {
        // 參數(shù)校驗(yàn)邏輯
    }
    
    protected void validateStock(Order order) {
        // 庫(kù)存校驗(yàn)邏輯：檢查庫(kù)存是否充足
        if (getStockCount(order.getProductId()) < order.getQuantity()) {
            throw new InsufficientStockException("庫(kù)存不足");
        }
    }
    
    // 其他方法實(shí)現(xiàn)...
}

// 子類錯(cuò)誤覆蓋父類校驗(yàn)邏輯
public class FlashSaleOrderProcessor extends OrderProcessor {
    @Override
    protected void validateStock(Order order) {
        // 為"提高性能"，去掉了庫(kù)存校驗(yàn)
        log.info("跳過(guò)庫(kù)存校驗(yàn)，直接處理秒殺訂單");
    }
}

public abstract class OrderProcessor {
    // 用final修飾核心流程，防止子類覆蓋
    public final void process(Order order) {
        validateParams(order);
        // 核心校驗(yàn)邏輯用private修飾，完全禁止子類修改
        doValidateStock(order);
        deductStock(order);
        createOrder(order);
        // 提供擴(kuò)展點(diǎn)，允許子類添加額外處理
        afterProcess(order);
    }
    
    private void doValidateStock(Order order) {
        // 核心庫(kù)存校驗(yàn)邏輯，子類無(wú)法修改
        if (getStockCount(order.getProductId()) < order.getQuantity()) {
            throw new InsufficientStockException("庫(kù)存不足");
        }
    }
    
    // 提供鉤子方法，允許子類實(shí)現(xiàn)額外邏輯
    protected void afterProcess(Order order) {
        // 空實(shí)現(xiàn)，子類可根據(jù)需要重寫
    }
    
    // 其他方法保持不變...
}

public class FlashSaleOrderProcessor extends OrderProcessor {
    @Override
    protected void afterProcess(Order order) {
        // 僅在核心流程完成后添加秒殺場(chǎng)景的額外邏輯
        sendSeckillSuccessMessage(order.getUserId());
    }
}

public class PaymentChannel {
    private String channelConfig;
    
    public PaymentChannel(String channelId) {
        // 在構(gòu)造方法中執(zhí)行網(wǎng)絡(luò)請(qǐng)求
        this.channelConfig = fetchChannelConfig(channelId);
    }
    
    private String fetchChannelConfig(String channelId) {
        // 調(diào)用遠(yuǎn)程接口獲取配置
        try {
            return restTemplate.getForObject("/config/" + channelId, String.class);
        } catch (Exception e) {
            // 異常被捕獲，導(dǎo)致對(duì)象看似創(chuàng)建成功但狀態(tài)異常
            log.error("獲取支付渠道配置失敗", e);
            return null;
        }
    }
}

public class PaymentChannel {
    private final String channelConfig;
    
    // 私有構(gòu)造方法，確保只能通過(guò)工廠方法創(chuàng)建
    private PaymentChannel(String channelConfig) {
        this.channelConfig = channelConfig;
    }
    
    // 工廠方法負(fù)責(zé)初始化邏輯
    public static PaymentChannel create(String channelId) {
        String config = fetchChannelConfig(channelId);
        if (config == null) {
            throw new ChannelInitException("支付渠道初始化失敗");
        }
        return new PaymentChannel(config);
    }
    
    private static String fetchChannelConfig(String channelId) {
        try {
            return restTemplate.getForObject("/config/" + channelId, String.class);
        } catch (Exception e) {
            log.error("獲取支付渠道配置失敗", e);
            return null;
        }
    }
}

// 使用方式
try {
    PaymentChannel alipay = PaymentChannel.create("alipay");
    // 正常使用
} catch (ChannelInitException e) {
    // 優(yōu)雅處理初始化失敗
    log.error("初始化支付寶渠道失敗", e);
    // 可以切換到備用渠道
}

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class PermissionManager {
    protected List<String> permissions = new ArrayList<>();
    
    public List<String> getPermissions() {
        // 父類返回可修改的集合
        return permissions;
    }
    
    public void addPermission(String permission) {
        permissions.add(permission);
    }
}

public class ReadOnlyPermissionManager extends PermissionManager {
    @Override
    public List<String> getPermissions() {
        // 子類返回不可變集合
        return Collections.unmodifiableList(permissions);
    }
}

// 調(diào)用者代碼
PermissionManager manager = new ReadOnlyPermissionManager();
manager.getPermissions().add("admin:delete"); // 運(yùn)行時(shí)拋出UnsupportedOperationException

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class PermissionManager {
    protected List<String> permissions = new ArrayList<>();
    
    public List<String> getPermissions() {
        return new ArrayList<>(permissions); // 返回副本，防止外部修改
    }
    
    public void addPermission(String permission) {
        permissions.add(permission);
    }
}

// 使用組合而非繼承
public class ReadOnlyPermissionWrapper {
    private final PermissionManager manager;
    
    public ReadOnlyPermissionWrapper(PermissionManager manager) {
        this.manager = manager;
    }
    
    // 明確返回不可變集合
    public List<String> getPermissions() {
        return Collections.unmodifiableList(manager.getPermissions());
    }
    
    // 不提供addPermission方法，明確表示只讀特性
}

// 使用方式
PermissionManager manager = new PermissionManager();
ReadOnlyPermissionWrapper readOnlyManager = new ReadOnlyPermissionWrapper(manager);
// 調(diào)用者無(wú)法獲取到可修改的集合，避免了運(yùn)行時(shí)異常

public class ConfigClient {
    // 靜態(tài)變量A
    private static final String SERVER_URL = getServerUrlFromEnv();
    // 靜態(tài)變量B依賴A
    private static final ConfigConnector connector = new ConfigConnector(SERVER_URL);
    
    static {
        // 靜態(tài)塊中使用connector
        connector.init();
    }
    
    private static String getServerUrlFromEnv() {
        // 從環(huán)境變量獲取配置中心地址
        return System.getenv("CONFIG_SERVER_URL");
    }
}

public class ConfigConnector {
    private final String serverUrl;
    
    public ConfigConnector(String serverUrl) {
        this.serverUrl = serverUrl;
    }
    
    public void init() {
        // 初始化連接
        if (serverUrl == null) {
            throw new NullPointerException("serverUrl is null");
        }
        // 其他初始化邏輯...
    }
}

public class ConfigClient {
    private static final ConfigConnector connector;
    
    // 靜態(tài)塊中統(tǒng)一處理初始化
    static {
        ConfigConnector tempConnector = null;
        try {
            String serverUrl = getServerUrlFromEnv();
            if (serverUrl == null) {
                // 提供默認(rèn)值或拋出明確異常
                serverUrl = "http://default-config-server:8888";
                log.warn("未配置CONFIG_SERVER_URL，使用默認(rèn)值: {}", serverUrl);
            }
            tempConnector = new ConfigConnector(serverUrl);
            tempConnector.init();
        } catch (Exception e) {
            log.error("配置中心初始化失敗", e);
            // 根據(jù)業(yè)務(wù)需求決定是否允許應(yīng)用繼續(xù)啟動(dòng)
            // 此處選擇允許啟動(dòng)，但connector保持為null
        }
        connector = tempConnector;
    }
    
    // 靜態(tài)工廠方法提供實(shí)例
    public static ConfigConnector getConnector() {
        if (connector == null) {
            throw new IllegalStateException("配置中心未初始化成功");
        }
        return connector;
    }
    
    private static String getServerUrlFromEnv() {
        return System.getenv("CONFIG_SERVER_URL");
    }
}