public static void demo(){
		Cache<String,String> cache = Caffeine.newBuilder()
			.expireAfterWrite(20, TimeUnit.SECONDS)
			.maximumSize(5000)
			.build();
		// 1.Insert or update an entry
		cache.put("hello","world");
		// 2. Lookup an entry, or null if not found
		String val1 = cache.getIfPresent("hello");
		// 3. Lookup and compute an entry if absent, or null if not computable
		cache.get("msg", k -> createExpensiveGraph(k));
		// 4. Remove an entry
		cache.invalidate("hello");
	}
	private static String createExpensiveGraph(String key){
		System.out.println("begin to query db..."+Thread.currentThread().getName());
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
		}
		System.out.println("success to query db...");
		return UUID.randomUUID().toString();
	}

private static void demo() {
		LoadingCache<String, String> cache = Caffeine.newBuilder()
			.expireAfterWrite(5, TimeUnit.SECONDS)
			.maximumSize(500)
			.build(new CacheLoader<String, String>() {
				@Override
				public String load(String key) throws Exception {
					return createExpensiveGraph(key);
				}
				@Override
				public Map<String, String>  loadAll(Iterable<? extends String> keys) {
					System.out.println("build keys");
					Map<String,String> map = new HashMap<>();
					for(String k : keys){
						map.put(k,k+"-val");
					}
					return map;
				}
			});
		String val1 = cache.get("hello");
		Map<String,String> values = cache.getAll(Lists.newArrayList("key1", "key2"));
	}
	private static String createExpensiveGraph(String key){
		System.out.println("begin to query db..."+Thread.currentThread().getName());
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
		}
		System.out.println("success to query db...");
		return UUID.randomUUID().toString();
	}

public interface CacheLoader<K, V>{
    V load(@NonNull K var1) throws Exception;
    Map<K, V> loadAll(@NonNull Iterable<? extends K> keys);
}  

private static void demo() throws ExecutionException, InterruptedException {
		AsyncCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(500)
			.expireAfterWrite(10, TimeUnit.SECONDS)
			.buildAsync();
		// Lookup and asynchronously compute an entry if absent
		CompletableFuture<String> future = cache.get("hello", k -> createExpensiveGraph(k));
		System.out.println(future.get());
	}
	private static String createExpensiveGraph(String key){
		System.out.println("begin to query db..."+Thread.currentThread().getName());
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
		}
		System.out.println("success to query db...");
		return UUID.randomUUID().toString();
	}

public static void demo() throws ExecutionException, InterruptedException {
		AsyncLoadingCache<String,String> cache = Caffeine.newBuilder()
			.expireAfterWrite(10, TimeUnit.SECONDS)
			.maximumSize(500)
			.buildAsync(k -> createExpensiveGraph(k));
		CompletableFuture<String> future = cache.get("hello");
		System.out.println(future.get());
	}
	private static String createExpensiveGraph(String key){
		System.out.println("begin to query db..."+Thread.currentThread().getName());
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
		}
		System.out.println("success to query db...");
		return UUID.randomUUID().toString();
	}

LoadingCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(500)
			.recordStats()
			.build( k -> UUID.randomUUID().toString());
		for (int i = 0; i < 600; i++) {
			cache.get(String.valueOf(i));
			if(i> 500){
				CacheStats stats = cache.stats();
				System.out.println("evictionCount:"+stats.evictionCount());
				System.out.println("stats:"+stats.toString());
			}
		}

LoadingCache<Integer,String> cache = Caffeine.newBuilder()
			.maximumWeight(300)
			.recordStats()
			.weigher((Weigher<Integer, String>) (key, value) -> {
				if(key % 2 == 0){
					return 2;
				}
				return 1;
			})
			.build( k -> UUID.randomUUID().toString());
		for (int i = 0; i < 300; i++) {
			cache.get(i);
			if(i> 200){
				System.out.println(cache.stats().toString());
			}
		}

private static LoadingCache<String,String> cache = Caffeine.newBuilder()
		.expireAfterAccess(1, TimeUnit.SECONDS)
		.build(key -> UUID.randomUUID().toString());

private static LoadingCache<String,String> cache = Caffeine.newBuilder()
		.expireAfterWrite(1, TimeUnit.SECONDS)
		.build(key -> UUID.randomUUID().toString());

private static LoadingCache<String,String> cache = Caffeine.newBuilder()
		.refreshAfterWrite(1, TimeUnit.SECONDS)
		.build(key -> UUID.randomUUID().toString());

public static void demo(){
		MyTicker ticker = new MyTicker();
		LoadingCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(500)
			.ticker(ticker)
			//此時(shí)的效果為expireAfterWrite(5,TimeUnit.SECONDS)
			.expireAfter(new Expiry<String, String>() {
				//1.如果寫(xiě)入key時(shí)是第一次創(chuàng)建，則調(diào)用該方法返回key剩余的超時(shí)時(shí)間, 單位納秒ns
				//currentTime為當(dāng)前put時(shí)Ticket的時(shí)間，單位ns
				@Override
				public long expireAfterCreate(String key,String value, long currentTime) {
					System.out.println("write first currentTime:"+currentTime/1_000_000_000L);
					return 5_000_000_000L;//5s
				}
				//2.如果寫(xiě)入key時(shí)已經(jīng)存在即更新key時(shí)，則調(diào)用該方法返回key剩余的超時(shí)時(shí)間, 單位納秒ns
				//currentTime為當(dāng)前put時(shí)Ticket的時(shí)間，單位ns，durationTime為舊值(上次設(shè)置)剩余的存活時(shí)間，單位是ns
				@Override
				public long expireAfterUpdate(String key,String value, long currentTime,long durationTime) {
					System.out.println("update currentTime:"+currentTime/1_000_000_000L+",leftTime:"+durationTime/1_000_000_000L);
					return 5_000_000_000L;//5s
				}
				//3.如果key被訪問(wèn)時(shí),則調(diào)用該方法返回key剩余的超時(shí)時(shí)間, 單位納秒ns
				//currentTime為read時(shí)Ticket的時(shí)間，單位ns，durationTime為舊值(上次設(shè)置)剩余的存活時(shí)間，單位是ns
				@Override
				public long expireAfterRead(String key,String value, long currentTime,long durationTime) {
					System.out.println("read currentTime:"+currentTime/1_000_000_000L+",leftTime:"+durationTime/1_000_000_000L);
					return durationTime;
				}
			})
			.build(k ->  UUID.randomUUID().toString());
		cache.get("key1");//觸發(fā)expireAfterCreate
		ticker.advance(1, TimeUnit.SECONDS);//模擬時(shí)間消逝
		cache.get("key1");//觸發(fā)expireAfterRead,剩余生存時(shí)間4s
		ticker.advance(2, TimeUnit.SECONDS);//模擬時(shí)間消逝
		cache.put("key1","value1");//觸發(fā)expireAfterUpdate,重置生存時(shí)間為5s
		ticker.advance(3, TimeUnit.SECONDS);//模擬時(shí)間消逝
		cache.get("key1");//觸發(fā)expireAfterCreate,剩余生存時(shí)間為2s
	}
public class MyTicker implements Ticker {
	private final AtomicLong nanos = new AtomicLong();
	//模擬時(shí)間消逝
	public void advance(long time, TimeUnit unit) {
		this.nanos.getAndAdd(unit.toNanos(time));
	}
	@Override
	public long read() {
		return this.nanos.get();
	}
}

/**
	 * 允許GC時(shí)回收keys或values
	 */
	public static void demo(){
		LoadingCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(500)
			.expireAfterWrite(10, TimeUnit.SECONDS)
			.weakKeys()
			.weakValues()
			.build(k -> UUID.randomUUID().toString());
	}

public static void demo(){
		/**
		 * 使用軟引用存儲(chǔ)value,GC內(nèi)存不夠時(shí)會(huì)回收
		 */
		LoadingCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(500)
			.expireAfterWrite(10, TimeUnit.SECONDS)
			.softValues()//注意沒(méi)有softKeys方法
			.build(k -> UUID.randomUUID().toString());
	}

// individual key
cache.invalidate(key)
// bulk keys
cache.invalidateAll(keys)
// all keys
cache.invalidateAll()

public static void demo(){
		LoadingCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(5)
			.recordStats()
			.expireAfterWrite(2, TimeUnit.SECONDS)
			.removalListener((String key, String value, RemovalCause cause) -> {
				System.out.printf("Key %s was removed (%s)%n", key, cause);
			})
			.build(key -> UUID.randomUUID().toString());
		for (int i = 0; i < 15; i++) {
			cache.get(i+"");
			try {
				Thread.sleep(200);
			} catch (InterruptedException e) {
			}
		}
		//因?yàn)閑vict是異步線程去執(zhí)行，為了看到效果稍微停頓一下
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
		}
	}

public static void demo(){
		LoadingCache<Integer,String> cache = Caffeine.newBuilder()
			.maximumSize(10)
			.expireAfterWrite(10, TimeUnit.SECONDS)
			.recordStats()
			.build(key -> {
				if(key % 6 == 0 ){
					return null;
				}
				return  UUID.randomUUID().toString();
			});
		for (int i = 0; i < 20; i++) {
			cache.get(i);
			printStats(cache.stats());
		}
		for (int i = 0; i < 10; i++) {
			cache.get(i);
			printStats(cache.stats());
		}
	}
	private static void printStats(CacheStats stats){
		System.out.println("---------------------");
		System.out.println("stats.hitCount():"+stats.hitCount());//命中次數(shù)
		System.out.println("stats.hitRate():"+stats.hitRate());//緩存命中率
		System.out.println("stats.missCount():"+stats.missCount());//未命中次數(shù)
		System.out.println("stats.missRate():"+stats.missRate());//未命中率
		System.out.println("stats.loadSuccessCount():"+stats.loadSuccessCount());//加載成功的次數(shù)
		System.out.println("stats.loadFailureCount():"+stats.loadFailureCount());//加載失敗的次數(shù),返回null
		System.out.println("stats.loadFailureRate():"+stats.loadFailureRate());//加載失敗的百分比
		System.out.println("stats.totalLoadTime():"+stats.totalLoadTime());//總加載時(shí)間,單位ns
		System.out.println("stats.evictionCount():"+stats.evictionCount());//驅(qū)逐次數(shù)
		System.out.println("stats.evictionWeight():"+stats.evictionWeight());//驅(qū)逐的weight值總和
		System.out.println("stats.requestCount():"+stats.requestCount());//請(qǐng)求次數(shù)
		System.out.println("stats.averageLoadPenalty():"+stats.averageLoadPenalty());//單次load平均耗時(shí)
	}

public static void demo(){
		MyTicker ticker = new MyTicker();
		LoadingCache<String,String> cache = Caffeine.newBuilder()
			.maximumSize(500)
			.ticker(ticker)
			.expireAfterWrite(1, TimeUnit.SECONDS)
			.build(k ->  UUID.randomUUID().toString());
		cache.get("key1");//觸發(fā)expireAfterCreate
		ticker.advance(1, TimeUnit.SECONDS);//模擬時(shí)間消逝
		cache.get("key1");//觸發(fā)expireAfterRead,剩余生存時(shí)間4s
		ticker.advance(2, TimeUnit.SECONDS);//模擬時(shí)間消逝
		cache.put("key1","value1");//觸發(fā)expireAfterUpdate,重置生存時(shí)間為5s
	}
public class MyTicker implements Ticker {
	private final AtomicLong nanos = new AtomicLong();
	//模擬時(shí)間消逝
	public void advance(long time, TimeUnit unit) {
		this.nanos.getAndAdd(unit.toNanos(time));
	}
	@Override
	public long read() {
		return this.nanos.get();
	}
}