Google Guava -缓存cache简单使用

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package guavacache;<br> import java.util.concurrent.ExecutionException; import java.util.concurrent.TimeUnit;   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 cachetest {     public static class Student {         private int id;         public String name;           public int getId() {             return id;         }           public void setId(int id) {             this.id = id;         }           public String getName() {             return name;         }           public void setName(String name) {             this.name = name;         }           @Override         public String toString() {             return id + "| " + name;         }     }       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());     }   }

　　测试最大容量LRU算法, 感觉更像是把使用时间最近的保留

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Student student = studentCache.get(1); System.out.println(student); student = studentCache.get(1); System.out.println(student); student = studentCache.get(1); System.out.println(student);   student = studentCache.get(2); System.out.println(student);   student = studentCache.get(3); System.out.println(student);

　　结果为 1 was removed, cause is SIZE

maven 

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<dependency>     <groupId>com.google.guava</groupId>     <artifactId>guava</artifactId>     <version>18.0</version> </dependency>