Google Guava -緩存cache簡單使用

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 {
		// 緩存接口這里是LoadingCache，LoadingCache在緩存項不存在時可以自動加載緩存
		LoadingCache<Integer, Student> studentCache
		// CacheBuilder的構造函數是私有的，只能通過其靜態方法newBuilder()來獲得CacheBuilder的實例
				= CacheBuilder.newBuilder()
						// 設置並發級別為8，並發級別是指可以同時寫緩存的線程數
						.concurrencyLevel(8)
						// 設置寫緩存后8秒鍾過期
						.expireAfterWrite(18, TimeUnit.SECONDS)
						// 設置緩存容器的初始容量為10
						.initialCapacity(2)
						// 設置緩存最大容量為100，超過100之后就會按照LRU最近雖少使用算法來移除緩存項
						.maximumSize(2)
						// 設置要統計緩存的命中率
						.recordStats()
						// 設置緩存的移除通知
						.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，在緩存不存在時通過CacheLoader的實現自動加載緩存
						.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++) {
//			// 從緩存中得到數據，由於我們沒有設置過緩存，所以需要通過CacheLoader加載緩存數據
//			Student student = studentCache.get(i);
//			System.out.println(student);
//			// 休眠1秒
//			TimeUnit.SECONDS.sleep(1);
//		}
				

		System.out.println("cache stats:");
		// 最后打印緩存的命中率等 情況
		System.out.println(studentCache.stats().toString());
	}

}

　　測試最大容量LRU算法, 感覺更像是把使用時間最近的保留

		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);

　　結果為 1 was removed, cause is SIZE

maven 

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