Guava Cache

• 单应用、本地缓存
• 依赖

		<dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>30.1-jre</version> </dependency>

• 示例

import com.google.common.cache.*;import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;public class LocalCache {public static void main(String[] args) throws ExecutionException {
//     LoadingCache 在缓存项不存在时可以自动加载缓存LoadingCache<String,Object> loadingCache
//               CacheBuilder 构造私有，只能通过静态方法 newBuilder()来获取CacheBuilder的实例= (LoadingCache<String, Object>) CacheBuilder.newBuilder()
//                设置并发级别8；同时写缓存的线程数为8.concurrencyLevel(8)
//                写缓存后8秒过期.expireAfterWrite(8, TimeUnit.SECONDS)
//                写缓存后1秒刷新.refreshAfterWrite(1,TimeUnit.SECONDS)
//                缓存初始容量 10.initialCapacity(10)
//                缓存最大容量100，超过100之后会按照LRU最近最少使用算法移除缓存项.maximumSize(100)
//                设置要统计缓存的命中率.recordStats()
//                缓存的移除通知.removalListener(new RemovalListener<String, Object>() {@Overridepublic void onRemoval(RemovalNotification<String, Object> removalNotification) {System.out.println(removalNotification.getKey() + "被移除，原因：" + removalNotification.getCause());}}).build(new CacheLoader<String, Object>() {@Overridepublic Object load(String key) throws Exception {System.out.println("缓存不存在时，从数据加载"+key);
//                                todo 记载数据,返回对应数据return new Object();}});
//        第一次读取,会加载数据for (int i = 0; i < 20; i++) {Object o = loadingCache.get(i + "");System.out.println(o);}
//        第二次读取，直接用for (int i = 0; i < 20; i++) {Object o = loadingCache.get(i + "");System.out.println(o);}System.out.println("缓存命中率："+loadingCache.stats());}
}