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Java并发程序设计(7)线程池之异常终止和正常关闭
1.1. 线程池中的线程的异常终止
如果线程池中的线程的任务代码发生异常导致线程终止,线程池会自动创建一个新线程。
对于各种类型的线程池,都是如此。以下代码在单个线程的线程池中抛出一个异常,可以发现后续任务中输出的每个tid的值都不相同。
ExecutorService executorService = Executors.newSingleThreadExecutor(); for(int j=0;j<10;j++){ final int t = j; executorService.execute( new Runnable(){ @Override public void run() { for(int i=0;i<4;i++){ System.out.println("t:" + t + "," + "i:" + i + ", tid:" + Thread.currentThread().getId()); int a = 3 /0;//产生/ by zero异常,线程终止。新任务将创建新线程。 } } }); }
输出信息中可以看到对每个任务(t),线程id(tid)都不同。
t:0,i:0, tid:8
t:1,i:0, tid:10
Exception in thread "pool-1-thread-1" t:2,i:0, tid:11
Exception in thread "pool-1-thread-2" Exception in thread "pool-1-thread-3" java.lang.ArithmeticException: / by zero
t:3,i:0, tid:12
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception in thread "pool-1-thread-4" java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
t:4,i:0, tid:13
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
t:5,i:0, tid:14
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
t:6,i:0, tid:15
Exception in thread "pool-1-thread-6" Exception in thread "pool-1-thread-5" Exception in thread "pool-1-thread-7" java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
t:7,i:0, tid:16
at java.lang.Thread.run(Unknown Source)
java.lang.ArithmeticException: / by zero
t:8,i:0, tid:17 at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception in thread "pool-1-thread-9" Exception in thread "pool-1-thread-8" java.lang.ArithmeticException: / by zero
t:9,i:0, tid:18 at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Exception in thread "pool-1-thread-10" java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
java.lang.ArithmeticException: / by zero
at com.test.concurrence.ThreadPoolTest$3.run(ThreadPoolTest.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
1.2. 线程池的终止
shutdownNow()和shutdown()都可以终止线程池,两者都可以终止线程池,阻止新任务的提交。
shutdownNow()会停止当前正在执行的任务,清除已提交但是尚未运行的任务,然后终止线程池。
shutdown()会等待已经提交的所有任务执行完毕才终止线程池。
ExecutorService executorService = Executors.newFixedThreadPool(2); for(int j=0;j<10;j++){ final int t = j; executorService.execute( new Runnable(){ @Override public void run() { for(int i=0;i<4;i++){ String s = "t:" + t + "," + "i:" + i + ", tid:" + Thread.currentThread().getId(); System.out.println(s); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } }); } executorService.shutdownNow();
t:0,i:0, tid:8
end.
t:1,i:0, tid:9
java.lang.InterruptedException: sleep interrupted
t:0,i:1, tid:8
at java.lang.Thread.sleep(Native Method)
at com.test.concurrence.ThreadPoolTest$1.run(ThreadPoolTest.java:27)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.test.concurrence.ThreadPoolTest$1.run(ThreadPoolTest.java:27)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
t:1,i:1, tid:9
t:0,i:2, tid:8
t:1,i:2, tid:9
t:0,i:3, tid:8
t:1,i:3, tid:9
Java并发程序设计(7)线程池之异常终止和正常关闭