java中实现缓存的几种方式

在Java中实现缓存的几种方式包括：

1. 使用HashMap：

public class Cache<K, V> {
    private final Map<K, V> cache = new HashMap<>();
 
    public V get(K key) {
        return cache.get(key);
    }
 
    public void put(K key, V value) {
        cache.put(key, value);
    }
}

2. 使用Guava Cache：

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
 
public class GuavaCacheExample {
    private static final LoadingCache<String, String> cache = CacheBuilder.newBuilder()
        .maximumSize(1000)
        .expireAfterWrite(10, TimeUnit.MINUTES)
        .build(new CacheLoader<String, String>() {
            @Override
            public String load(String key) throws Exception {
                return fetchDataFromDatabase(key);
            }
        });
 
    public static String get(String key) {
        try {
            return cache.get(key);
        } catch (ExecutionException e) {
            e.printStackTrace();
            return null;
        }
    }
 
    private static String fetchDataFromDatabase(String key) {
        // 从数据库获取数据
        return "data";
    }
}

3. 使用Ehcache：

import net.sf.ehcache.Cache;
import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Element;
 
public class EhCacheExample {
    private static final CacheManager cacheManager = CacheManager.newInstance();
    private static final Cache cache = cacheManager.getCache("myCache");
 
    public static String get(String key) {
        Element element = cache.get(key);
        return element != null ? (String) element.getObjectValue() : null;
    }
 
    public static void put(String key, String value) {
        cache.put(new Element(key, value));
    }
}

4. 使用Caffeine：

import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
 
public class CaffeineCacheExample {
    private static final Cache<String, String> cache = Caffeine.newBuilder()
        .maximumSize(1000)
        .expireAfterWrite(10, TimeUnit.MINUTES)
        .build();
 
    public static String get(String key) {
        return cache.get(key, k -> fetchDataFromDatabase(key));
    }
 
    private static String fetchDataFromDatabase(String key) {
        // 从数据库获取数据
        return "data";
    }
}

这些方式可以实现不同层次的缓存需求，从简单的HashMap到复杂的分布式缓存解决方案如Ehcache和\`Caffeine