Google Guava -缓存cache简单使用

原文地址：https://www.cnblogs.com/chengxin1982/p/6427663.html

Google Guava -缓存cache简单使用

public static void main(String[] args) throws ExecutionException, InterruptedException {

        // 缓存接口这里是LoadingCache，LoadingCache在缓存项不存在时可以自动加载缓存

        LoadingCache<Integer, Student> studentCache

        // CacheBuilder的构造函数是私有的，只能通过其静态方法newBuilder()来获得CacheBuilder的实例

                = CacheBuilder.newBuilder()

                        // 设置并发级别为8，并发级别是指可以同时写缓存的线程数

                        .concurrencyLevel(8)

                        // 设置写缓存后8秒钟过期

                        .expireAfterWrite(18, TimeUnit.SECONDS)

                        // 设置缓存容器的初始容量为10

                        .initialCapacity(2)

                        // 设置缓存最大容量为100，超过100之后就会按照LRU最近虽少使用算法来移除缓存项

                        .maximumSize(2)

                        // 设置要统计缓存的命中率

                        .recordStats()

                        // 设置缓存的移除通知

                        .removalListener(new RemovalListener<Object, Object>() {

                            public void onRemoval(RemovalNotification<Object, Object> notification) {

                                System.out.println(

                                        notification.getKey() + " was removed, cause is " + notification.getCause());

                            }

                        })

                        // build方法中可以指定CacheLoader，在缓存不存在时通过CacheLoader的实现自动加载缓存

                        .build(new CacheLoader<Integer, Student>() {

                            @Override

                            public Student load(Integer key) throws Exception {

                                System.out.println("load student " + key);

                                Student student = new Student();

                                student.setId(key);

                                student.setName("name " + key);

                                return student;

                            }

                        });

//      for (int i = 0; i < 20; i++) {

//          // 从缓存中得到数据，由于我们没有设置过缓存，所以需要通过CacheLoader加载缓存数据

//          Student student = studentCache.get(i);

//          System.out.println(student);

//          // 休眠1秒

//          TimeUnit.SECONDS.sleep(1);

//      }

        System.out.println("cache stats:");

        // 最后打印缓存的命中率等 情况

        System.out.println(studentCache.stats().toString());

    }