q.利用主程式呼叫多執行緒時, 要怎麼停止正在執行的多執行緒
ans. 在thread裡利用InterruptedException 把工作結束
例如這裡是for loop 10次, 就把工作數直接設定到滿
建立Car
每一台車工作量10次
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | public class Car implements Runnable { private String name; public Car(String name) { this.name = name; } @Override public void run() { for (int i = 0; i < 10; i++) { System.out.println(name + " move :" + i); try { Thread.sleep(1000); } catch (InterruptedException e) { System.out.println(name + " is interrupted."); i = 10; } } }} |
主程式
1 2 3 4 5 6 7 8 9 10 11 12 | Car toyota = new Car("toyota");Car ford = new Car("ford");Thread thread1 = new Thread(toyota);Thread thread2 = new Thread(ford);thread1.start();thread2.start();Thread.sleep(2000);thread2.interrupt();System.out.println("main job is done"); |
thread1, thread2 啟動後, 等待兩秒,
再呼叫thread2.interrupt() , 這樣執行緒收到interrupt, 就會以interrupted exception 處理, 終止工作
而另一支thread1 繼續進行
如果我想等所有的執行緒都結束, 再回到主程式, 則加上join()即可
因為interrupted exception也是讓該執行緒結束, 所以主程式還是視此子執行緒成功結束了
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | Car toyota = new Car("toyota");Car ford = new Car("ford");Thread thread1 = new Thread(toyota);Thread thread2 = new Thread(ford);thread1.start();thread2.start();Thread.sleep(2000);thread2.interrupt();thread2.join();thread1.join();System.out.println("main job is done"); |
如上
ford會在兩秒後中斷, 但主程式會繼續等待toyota跑完全部工作, 主程式再結束
ThreadGroup
如果我是想從另外一支程式停止特定的thread,則可以利用threadgroup
再取得符合threadgroup name的所有執行緒
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | Car toyota = new Car("toyota"); Car ford = new Car("ford"); ThreadGroup tg = new ThreadGroup("CarGroup"); Thread thread1 = new Thread(tg,toyota); Thread thread2 = new Thread(tg,ford); logger.info(tg.getName()); thread1.start(); thread2.start(); thread2.join(); thread1.join(); logger.info("main job is done"); |
request stop
1 2 3 4 5 6 7 8 9 | Map<Thread, StackTraceElement[]> threads = Thread.getAllStackTraces(); for (Map.Entry<Thread, StackTraceElement[]> entry : threads.entrySet()) { Thread thread = entry.getKey(); ThreadGroup threadGroup = thread.getThreadGroup(); if (threadGroup.getName().equals("CarGroup")) { threadGroup.interrupt(); } } |
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