java中runnable

去年年底，我正在運行預定的任務來監視Neo4j集群，而我遇到的問題之一是有時會退出監視。

最終我意識到這是因為RuntimeException被拋出到Runnable方法中，而我沒有處理它。 以下代碼演示了該問題：

import java.util.ArrayList; import java.util.List; import java.util.concurrent.*;public class RunnableBlog {public static void main(String[] args) throws ExecutionException, InterruptedException {ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();executor.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {System.out.println(Thread.currentThread().getName() + " -> " + System.currentTimeMillis());throw new RuntimeException("game over");}}, 0, 1000, TimeUnit.MILLISECONDS).get();System.out.println("exit");executor.shutdown();} }

如果運行該代碼，我們將看到RuntimeException，但是執行器不會退出，因為線程在沒有通知的情況下就死了：

Exception in thread "main" pool-1-thread-1 -> 1391212558074 java.util.concurrent.ExecutionException: java.lang.RuntimeException: game overat java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:252)at java.util.concurrent.FutureTask.get(FutureTask.java:111)at RunnableBlog.main(RunnableBlog.java:11)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:601)at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120) Caused by: java.lang.RuntimeException: game overat RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722)

當時我最終添加了一個try catch塊并打印如下異常：

public class RunnableBlog {public static void main(String[] args) throws ExecutionException, InterruptedException {ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();executor.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {try {System.out.println(Thread.currentThread().getName() + " -> " + System.currentTimeMillis());throw new RuntimeException("game over");} catch (RuntimeException e) {e.printStackTrace();}}}, 0, 1000, TimeUnit.MILLISECONDS).get();System.out.println("exit");executor.shutdown();} }

據我所知，這允許異常被識別，并且執行Runnable的線程不會死亡。

java.lang.RuntimeException: game over pool-1-thread-1 -> 1391212651955at RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722) pool-1-thread-1 -> 1391212652956 java.lang.RuntimeException: game overat RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722) pool-1-thread-1 -> 1391212653955 java.lang.RuntimeException: game overat RunnableBlog$1.run(RunnableBlog.java:16)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722)

這很好，使我能夠繼續監視集群。

但是，我最近開始閱讀“ Java Concurrency in Practice ”（購買后僅6年！），并且意識到這可能不是處理RuntimeException的正確方法。

public class RunnableBlog {public static void main(String[] args) throws ExecutionException, InterruptedException {ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();executor.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {try {System.out.println(Thread.currentThread().getName() + " -> " + System.currentTimeMillis());throw new RuntimeException("game over");} catch (RuntimeException e) {Thread t = Thread.currentThread();t.getUncaughtExceptionHandler().uncaughtException(t, e);}}}, 0, 1000, TimeUnit.MILLISECONDS).get();System.out.println("exit");executor.shutdown();} }

我看不到這兩種方法之間的差異很大，因此如果有人可以向我解釋為什么這種方法比我以前的捕獲異常并打印堆棧跟蹤的方法更好，那將是一個很好的選擇。

參考： Java：通過Mark Needham博客博客的JCG合作伙伴 Mark Needham在Runnable中處理RuntimeException 。

翻譯自: https://www.javacodegeeks.com/2014/02/java-handling-a-runtimeexception-in-a-runnable.html

java中runnable

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