Google Guava -缓存cache简单使用

package guavacache;

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

		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 

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