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

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

	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

	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

 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

  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();

            }
        }