Java並發程式設計(7)線程池之異常終止和正常關閉

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1.1. 線程池中的線程的異常終止

如果線程池中的線程的任務代碼發生異常導致線程終止，線程池會自動建立一個新線程。

對於各種類型的線程池，都是如此。以下代碼在單個線程的線程池中拋出一個異常，可以發現後續任務中輸出的每個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(){@Overridepublic void run() {for(int i=0;i<4;i++){System.out.println("t:" + t + "," + "i:" + i + ", tid:" + Thread.currentThread().getId());int a = 3 /0;//產生/ by zero異常，線程終止。新任務將建立新線程。}}});} 

 

輸出資訊中可以看到對每個任務(t)，線程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. 線程池的終止

shutdownNow()和shutdown()都可以終止線程池，兩者都可以終止線程池，阻止新任務的提交。

shutdownNow()會停止當前正在執行的任務，清除已提交但是尚未啟動並執行任務，然後終止線程池。

shutdown()會等待已經提交的所有任務執行完畢才終止線程池。

ExecutorService  executorService = Executors.newFixedThreadPool(2);for(int j=0;j<10;j++){final int t = j;executorService.execute( new Runnable(){@Overridepublic 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並發程式設計(7)線程池之異常終止和正常關閉