Guava 常用功能，防止阁下重复造轮子

本文主要是介绍Guava 常用功能，防止阁下重复造轮子，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1. 本地缓存

    /*** 功能：缓存* 文档：<a href="https://github.com/google/guava/wiki/CachesExplained">CachesExplained</a>*/@Testpublic void test_cache() {Cache<String, String> cache = CacheBuilder.newBuilder()// 最大存储条数，缓存将尝试逐出最近或不经常使用的条目.maximumSize(10000)// 可以设定删除时候的权重判断//.weigher((Weigher<String, String>) (x, y) -> x.length() - y.length())// 有效时间.expireAfterWrite(3, TimeUnit.SECONDS)// 记录次数.recordStats().build();cache.put("Lasse", "You are handsome.");log.info("测试结果：{}", cache.getIfPresent("Lasse"));cache.invalidate("Lasse"); // cache.invalidateAll(); 也可以全部删除log.info("测试结果：{}", cache.getIfPresent("Lasse"));log.info("测试结果：{}", cache.stats());}

2. MQ

    @Testpublic void test_eventbus() {EventBus eventBus = new EventBus();eventBus.register(new Listener());// 可以由其他服务推送消息，之后就可以在监听中收到了eventBus.post("消息总线，订单号：100001");}static class Listener {@Subscribepublic void handleEvent(String orderId) {log.info("测试结果：{}", orderId);}}

3. 并发回调

    /*** 功能：并发回调* 文档：https://github.com/google/guava/wiki/ListenableFutureExplained*/@Testpublic void test_ListenableFuture() throws InterruptedException {CountDownLatch countDownLatch = new CountDownLatch(1);ListeningExecutorService executorService = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(10));ListenableFuture<String> explosion = executorService.submit(() -> "finished");ExecutorService callBackService = Executors.newFixedThreadPool(1);Futures.addCallback(explosion, new FutureCallback<String>() {public void onSuccess(String explosion) {System.out.println("onSuccess");countDownLatch.countDown();}public void onFailure(Throwable thrown) {System.out.println("onFailure");countDownLatch.countDown();}}, callBackService);countDownLatch.await();}

4. 布隆过滤器

    /*** 功能：布隆过滤器* 文档：https://github.com/google/guava/wiki/HashingExplained#bloomfilter*/@Testpublic void test_BloomFilter() {BloomFilter<String> bloomFilter = BloomFilter.create(Funnels.stringFunnel(Charset.defaultCharset()),1000,0.01);// 向布隆过滤器中添加元素bloomFilter.put("apple");bloomFilter.put("banana");bloomFilter.put("orange");// 检查元素是否存在于布隆过滤器中System.out.println(bloomFilter.mightContain("apple"));   // trueSystem.out.println(bloomFilter.mightContain("banana"));  // trueSystem.out.println(bloomFilter.mightContain("orange"));  // trueSystem.out.println(bloomFilter.mightContain("grape"));   // false// 输出布隆过滤器的统计信息System.out.println("Expected FPP: " + bloomFilter.expectedFpp());System.out.println("Number of Inserted Elements: " + bloomFilter.approximateElementCount());}

5. 反射工具包

    /*** 功能：反射* 文档：https://github.com/google/guava/wiki/ReflectionExplained*/@Testpublic void test_Invokable() throws NoSuchMethodException {Method method = UserEntity.class.getMethod("getCreateTime");Invokable<?, ?> invokable = Invokable.from(method);log.info("测试结果 - 方法名称：{}", invokable.getName());log.info("测试结果 - 参数类型：{}", JSON.toJSONString(invokable.getTypeParameters()));log.info("测试结果 - 静态判断：{}", invokable.isStatic());// !(Modifier.isFinal(method.getModifiers()) || Modifiers.isPrivate(method.getModifiers()) || Modifiers.isStatic(method.getModifiers()) || Modifiers.isFinal(method.getDeclaringClass().getModifiers()))log.info("测试结果 - isOverridable：{}", invokable.isOverridable());}

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