import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
public class LoadingCacheExample {
    public static void main(String[] args) {
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(100) // 最大緩存項(xiàng)數(shù)
                .build(new CacheLoader<String, String>() {
                    @Override
                    public String load(String key) throws Exception {
                        return "Hello, " + key; // 定義緩存加載的方式
                    }
                });
        System.out.println(cache.getUnchecked("Guava")); // 輸出：Hello, Guava
    }
}

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import java.util.concurrent.ExecutionException;
public class LoadingCacheDemo {
    public static void main(String[] args) throws ExecutionException {
        // 創(chuàng)建一個(gè)CacheLoader
        CacheLoader<String, String> loader = new CacheLoader<String, String>() {
            @Override
            public String load(String key) {
                return key.toUpperCase(); // 模擬加載數(shù)據(jù)的過程
            }
        };
        // 使用CacheBuilder構(gòu)建一個(gè)LoadingCache
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(100) // 設(shè)置最大緩存數(shù)為100
                .build(loader);
        // 使用緩存
        System.out.println(cache.get("hello")); // 輸出: HELLO
        System.out.println(cache.get("guava")); // 輸出: GUAVA
    }
}

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
public class UserCache {
    // 假設(shè)有一個(gè)用戶服務(wù)，用于獲取用戶信息
    private static UserService userService = new UserService();
    public static void main(String[] args) throws Exception {
        // 創(chuàng)建CacheLoader
        CacheLoader<String, User> loader = new CacheLoader<String, User>() {
            @Override
            public User load(String userId) {
                // 從用戶服務(wù)獲取用戶信息
                return userService.getUserById(userId);
            }
        };
        // 創(chuàng)建LoadingCache
        LoadingCache<String, User> cache = CacheBuilder.newBuilder()
                .maximumSize(100) // 設(shè)置最大緩存數(shù)
                .build(loader);
        // 使用緩存獲取用戶信息
        User user = cache.get("123"); // 如果緩存中沒有，會調(diào)用load方法加載數(shù)據(jù)
        System.out.println(user);
    }
}

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import java.util.concurrent.TimeUnit;
public class AutoRefreshCache {
    public static void main(String[] args) throws Exception {
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .refreshAfterWrite(1, TimeUnit.MINUTES) // 設(shè)置1分鐘后刷新
                .build(new CacheLoader<String, String>() {
                    @Override
                    public String load(String key) {
                        return fetchDataFromDatabase(key); // 模擬從數(shù)據(jù)庫加載數(shù)據(jù)
                    }
                });
        // 使用緩存
        System.out.println(cache.get("key1")); // 第一次加載
        // 1分鐘后，嘗試再次獲取，將觸發(fā)刷新操作
    }
    private static String fetchDataFromDatabase(String key) {
        // 模擬數(shù)據(jù)庫操作
        return "Data for " + key;
    }
}

public class ExceptionHandlingCache {
    public static void main(String[] args) throws Exception {
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .build(new CacheLoader<String, String>() {
                    @Override
                    public String load(String key) throws Exception {
                        if ("errorKey".equals(key)) {
                            throw new Exception("Loading error");
                        }
                        return "Data for " + key;
                    }
                });

        try {
            System.out.println(cache.get("errorKey"));
        } catch (Exception e) {
            System.out.println("Error during cache load: " + e.getMessage());
        }
    }
}

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.cache.RemovalListener;
import com.google.common.cache.RemovalNotification;
public class CacheMonitoring {
    public static void main(String[] args) throws Exception {
        RemovalListener<String, String> removalListener = new RemovalListener<String, String>() {
            @Override
            public void onRemoval(RemovalNotification<String, String> notification) {
                System.out.println("Removed: " + notification.getKey() + ", Cause: " + notification.getCause());
            }
        };
        LoadingCache<String, String> cache = CacheBuilder.newBuilder()
                .maximumSize(100)
                .removalListener(removalListener)
                .build(new CacheLoader<String, String>() {
                    // ...
                });
        // 使用緩存
        // ...
    }
}

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .maximumSize(1000) // 設(shè)置最大緩存項(xiàng)為1000
        .build(new CacheLoader<String, String>() {
            // ...
        });

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .expireAfterWrite(10, TimeUnit.MINUTES) // 寫入后10分鐘過期
        .expireAfterAccess(5, TimeUnit.MINUTES) // 訪問后5分鐘過期
        .build(new CacheLoader<String, String>() {
            // ...
        });

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .build(new CacheLoader<String, String>() {
            @Override
            public String load(String key) throws Exception {
                try {
                    return fetchData(key);
                } catch (Exception e) {
                    // 處理異常
                }
            }
        });

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .softValues() // 使用軟引用存儲值
        .weakKeys() // 使用弱引用存儲鍵
        .build(new CacheLoader<String, String>() {
            // ...
        });

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .removalListener(notification -> {
            // 處理移除通知
        })
        .build(new CacheLoader<String, String>() {
            // ...
        });

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .build(key -> fetchDataFromDatabase(key)); // 使用Lambda表達(dá)式
private static String fetchDataFromDatabase(String key) {
    // 數(shù)據(jù)庫操作
    return "Data for " + key;
}

LoadingCache<String, User> userCache = //... 緩存初始化
List<String> userIds = //... 用戶ID列表
// 使用Stream API獲取用戶信息列表
List<User> users = userIds.stream()
        .map(userId -> userCache.getUnchecked(userId))
        .collect(Collectors.toList());

public Optional<User> getUser(String userId) {
    try {
        return Optional.ofNullable(userCache.get(userId));
    } catch (Exception e) {
        return Optional.empty();
    }
}

public class UserService {
    private final Map<String, Integer> loginCount = new ConcurrentHashMap<>();

    public int addLoginCount(String userId) {
        return loginCount.merge(userId, 1, Integer::sum);
    }
}

UserService userService = new UserService();

LoadingCache<String, Integer> loginCache = CacheBuilder.newBuilder()
        .expireAfterAccess(30, TimeUnit.MINUTES) // 設(shè)置緩存30分鐘后過期
        .build(new CacheLoader<String, Integer>() {
            @Override
            public Integer load(String userId) {
                return userService.addLoginCount(userId);
            }
        });

public void userLogin(String userId) {
    int count = loginCache.getUnchecked(userId);
    System.out.println("User " + userId + " login count: " + count);
}