震惊！这样终止线程，竟然会导致服务宕机？（下）

/**
 * Forces the thread to stop executing.
 * <p>
 * If there is a security manager installed, its <code>checkAccess</code>
 * method is called with <code>this</code>
 * as its argument. This may result in a
 * <code>SecurityException</code> being raised (in the current thread).
 * <p>
 * If this thread is different from the current thread (that is, the current
 * thread is trying to stop a thread other than itself), the
 * security manager's <code>checkPermission</code> method (with a
 * <code>RuntimePermission("stopThread")</code> argument) is called in
 * addition.
 * Again, this may result in throwing a
 * <code>SecurityException</code> (in the current thread).
 * <p>
 * The thread represented by this thread is forced to stop whatever
 * it is doing abnormally and to throw a newly created
 * <code>ThreadDeath</code> object as an exception.
 * <p>
 * It is permitted to stop a thread that has not yet been started.
 * If the thread is eventually started, it immediately terminates.
 * <p>
 * An application should not normally try to catch
 * <code>ThreadDeath</code> unless it must do some extraordinary
 * cleanup operation (note that the throwing of
 * <code>ThreadDeath</code> causes <code>finally</code> clauses of
 * <code>try</code> statements to be executed before the thread
 * officially dies).  If a <code>catch</code> clause catches a
 * <code>ThreadDeath</code> object, it is important to rethrow the
 * object so that the thread actually dies.
 * <p>
 * The top-level error handler that reacts to otherwise uncaught
 * exceptions does not print out a message or otherwise notify the
 * application if the uncaught exception is an instance of
 * <code>ThreadDeath</code>.
 *
 * @exception  SecurityException  if the current thread cannot
 *               modify this thread.
 * @see        #interrupt()
 * @see        #checkAccess()
 * @see        #run()
 * @see        #start()
 * @see        ThreadDeath
 * @see        ThreadGroup#uncaughtException(Thread,Throwable)
 * @see        SecurityManager#checkAccess(Thread)
 * @see        SecurityManager#checkPermission
 * @deprecated This method is inherently unsafe.  Stopping a thread with
 *       Thread.stop causes it to unlock all of the monitors that it
 *       has locked (as a natural consequence of the unchecked
 *       <code>ThreadDeath</code> exception propagating up the stack).  If
 *       any of the objects previously protected by these monitors were in
 *       an inconsistent state, the damaged objects become visible to
 *       other threads, potentially resulting in arbitrary behavior.  Many
 *       uses of <code>stop</code> should be replaced by code that simply
 *       modifies some variable to indicate that the target thread should
 *       stop running.  The target thread should check this variable
 *       regularly, and return from its run method in an orderly fashion
 *       if the variable indicates that it is to stop running.  If the
 *       target thread waits for long periods (on a condition variable,
 *       for example), the <code>interrupt</code> method should be used to
 *       interrupt the wait.
 *       For more information, see
 *       <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
 *       are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
 */
@Deprecated
public final void stop() {
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
        checkAccess();
        if (this != Thread.currentThread()) {
            security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
        }
    }
    // A zero status value corresponds to "NEW", it can't change to
    // not-NEW because we hold the lock.
    if (threadStatus != 0) {
        resume(); // Wake up thread if it was suspended; no-op otherwise
    }
    // The VM can handle all thread states
    stop0(new ThreadDeath());
}

// 自定义退出标识退出线程
static class FlagThread extends Thread {
    public volatile boolean exit = false;
    public void run() {
        while (!exit) {
            // 执行正常的业务逻辑
        }
    }
}

public class ThreadStopExample {
    public static void main(String[] args) throws InterruptedException {
        // 问题一：破坏了程序的完整性
        Thread t1 = new Thread(() -> {
            try {
                System.out.println("子线程开始执行");
                // 模拟业务处理
                Thread.sleep(1000);
            } catch (Exception e) { }
            // 伪代码：重要业务方法
            System.out.println("子线程的重要业务方法");
        });
        t1.start();
        // 让子线程先运行一点业务
        Thread.sleep(100);
        // 终止子线程
        t1.interrupt();
        // 等待一段时间，确保子线程“执行完”
        Thread.sleep(3000);
        System.out.println("主线程执行完成");
        // 问题二：破坏了原子逻辑
        MyThread myThread = new MyThread();
        Thread t2 = new Thread(myThread);
        // 开启线程
        t2.start();
        for (int i = 0; i < 10; i++) {
            Thread t = new Thread(myThread);
            t.start();
        }
        // 结束线程
        t2.interrupt();
    }
    /**
     * 自定义原子测试线程
     */
    static class MyThread implements Runnable {
        // 计数器
        int num = 0;
        @Override
        public void run() {
            // 同步代码块，保证原子操作
            synchronized (MyThread.class) {
                // 自增
                num++;
                try {
                    // 线程休眠 0.1 秒
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    System.out.println(e.getMessage());
                }
                // 自减
                num--;
                System.out.println(Thread.currentThread().getName() + " | num=" + num);
            }
        }
    }
}