java9

8.

关键是让它们拥有的监视器是同一对象，B方法前加synchronized，A方法的代码块部分加上synchronized(this)。

9.

public class Calculate extends Thread {
    public volatile boolean finished = false;
    public void run() {
        long count = 0;
        while (true) {
            count++;
            if (finished) {
                System.out.println(count);
                break;
            }
        }
    }

    public static void main(String[] args) {
        CalculatePrimes calculator = new CalculatePrimes();
        calculator.start();
        try {
Thread.sleep(10 * 1000);
} catch (InterruptedException e) {
            // fall through
        }
        calculator.finished = true;
    }
}