【Java 8 新特性】Java CompletableFuture supplyAsync() |
您所在的位置:网站首页 › turns怎么读的 › 【Java 8 新特性】Java CompletableFuture supplyAsync() |
Java CompletableFuture supplyAsync
与 thenApply() 一起使用自定义执行器 Executor与 whenComplete() 一起使用与流(Stream)一起使用参考文献
在此页面上,我们将提供
Java
CompletableFuture.supplyAsync()示例。
supplyAsync()是Java 8中引入的CompletableFuture静态方法。 方法supplyAsync()完成在ForkJoinPool.commonPool()或给定的Executor中异步运行的任务。 查找方法声明。 1.supplyAsync(Supplier supplier) 我们需要将Supplier作为任务传递给supplyAsync()方法。 默认情况下,该任务将在ForkJoinPool.commonPool()中异步完成运行,最后,supplyAsync()将返回新的CompletableFuture,其值是通过调用给定的Supplier所获得的值。 查找supplyAsync()方法的示例代码。 CompletableFuture cf = CompletableFuture.supplyAsync(()-> "Hello World!"); System.out.println(cf.get());2.supplyAsync(Supplier supplier, Executor executor) 我们需要将Supplier作为任务传递给supplyAsyncl()方法。 该任务将在给定的Executor中异步完成运行,最后supplyAsyncl()将返回具有通过调用给定Supplier所获得的值的新CompletableFuture。 使用Executor查找supplyAsyncl()的示例代码。 ExecutorService executorService = Executors.newSingleThreadExecutor(); CompletableFuture cf = CompletableFuture.supplyAsync( ()-> "Hello World!", executorService ); System.out.println(cf.get());在此页面上,我们将提供带有thenApply(),whenComplete()和ForkJoinPool.commonPool()和Executor的supplyAsync()示例。 我们还将通过Stream提供示例。 与 thenApply() 一起使用thenApply()通过传递阶段结果来执行一个函数。当我们将supplyAsync()与thenApply()一起使用时,那么thenApply()将通过将结果作为从supplyAsync()获得的参数传递来执行给定的函数。 SupplyAsyncExample1.java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutionException; public class SupplyAsyncExample1 { public static void main(String[] args) throws InterruptedException, ExecutionException { CompletableFuture cf = CompletableFuture.supplyAsync(()-> getDataById(10)) .thenApply(data -> sendData(data)); cf.get(); } private static String getDataById(int id) { System.out.println("getDataById: "+ Thread.currentThread().getName()); return "Data:"+ id; } private static String sendData(String data) { System.out.println("sendData: "+ Thread.currentThread().getName()); System.out.println(data); return data; } }输出 getDataById: ForkJoinPool.commonPool-worker-1 sendData: main Data:10主线程开始执行代码,当代码到达supplyAsync()时,supplyAsync()从ForkJoinPool.commonPool()获取新线程以异步执行其功能。 thenApply()将由主线程或supplyAsync()使用的线程执行。 如果supplyAsync()的Supplier花费的时间更长,则Apply()将由supplyAsync()所使用的线程执行,因此主线程将不会被阻塞。 要理解这一点,请按如下所示更改getDataById()方法。 private static String getDataById(int id) { System.out.println("getDataById: "+ Thread.currentThread().getName()); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } return "Data:"+ id; }输出 getDataById: ForkJoinPool.commonPool-worker-1 sendData: ForkJoinPool.commonPool-worker-1 Data:10 自定义执行器 Executor在这里,我们将Executor作为参数传递给supplyAsync() 。 现在,传递给supplyAsync() 的Supplier将由给定的Executor执行,而不是由ForkJoinPool.commonPool() 执行。 SupplyAsyncExample2.java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class SupplyAsyncExample2 { public static void main(String[] args) throws InterruptedException, ExecutionException { ExecutorService executorService = Executors.newSingleThreadExecutor(); CompletableFuture cf = CompletableFuture.supplyAsync( ()-> getDataById(10), executorService ) .thenApply(data -> sendData(data)); cf.get(); executorService.shutdown(); } private static String getDataById(int id) { System.out.println("getDataById: "+ Thread.currentThread().getName()); return "Data:"+ id; } private static String sendData(String data) { System.out.println("sendData: "+ Thread.currentThread().getName()); System.out.println(data); return data; } }输出 getDataById: pool-1-thread-1 sendData: main Data:10 与 whenComplete() 一起使用在这里,我们将使用whenComplete() 方法创建supplyAsync() 示例。 在完成给定操作后,whenComplete() 返回具有相同结果或异常的新CompletionStage。 行为是BiConsumer,其中第一个值是CompletionStage的结果,第二个是错误(如果有的话),否则为null。 SupplyAsyncExample3.java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutionException; public class SupplyAsyncExample3 { public static void main(String[] args) throws InterruptedException, ExecutionException { CompletableFuture cf = CompletableFuture.supplyAsync(()-> getDataById(10)) .whenComplete((data, error) -> { consumeData(data); if(error!= null) { System.out.println(error); } }); cf.get(); } private static String getDataById(int id) { System.out.println("getDataById: "+ Thread.currentThread().getName()); return "Data:"+ id; } private static void consumeData(String data) { System.out.println("consumeData: "+ Thread.currentThread().getName()); System.out.println(data); } }输出 getDataById: ForkJoinPool.commonPool-worker-1 consumeData: main Data:10 与流(Stream)一起使用查找带有Stream的supplyAsync()的示例。 SupplyAsyncExample4.java import java.util.Arrays; import java.util.List; import java.util.concurrent.CompletableFuture; public class SupplyAsyncExample4 { public static void main(String[] args) { List list = Arrays.asList(10, 20, 30); long count = list.stream().map(n-> CompletableFuture.supplyAsync(()-> getDataById(n))) .map(cf -> cf.thenApply(data -> sendData(data))) .map(t->t.join()).count(); System.out.println("Number of elements:"+ count); } private static String getDataById(int id) { System.out.println("getDataById: "+ Thread.currentThread().getName()); return "Data:"+ id; } private static String sendData(String data) { System.out.println("sendData: "+ Thread.currentThread().getName()); System.out.println(data); return data; } }输出 getDataById: ForkJoinPool.commonPool-worker-1 sendData: ForkJoinPool.commonPool-worker-1 Data:10 getDataById: ForkJoinPool.commonPool-worker-1 sendData: ForkJoinPool.commonPool-worker-1 Data:20 getDataById: ForkJoinPool.commonPool-worker-1 sendData: ForkJoinPool.commonPool-worker-1 Data:30 Number of elements:3 参考文献【1】CompletableFuture 【2】CompletionStage 【3】Java CompletableFuture supplyAsync() |
CopyRight 2018-2019 办公设备维修网 版权所有 豫ICP备15022753号-3 |