面试官问：如何中断一个线程，具体如何实现？（下）

class Example2 extends Thread {
    volatile boolean stop = false;// 线程中断信号量
    public static void main(String args[]) throws Exception {
        Example2 thread = new Example2();
        System.out.println("Starting thread...");
        thread.start();
        Thread.sleep(3000);
        System.out.println("Asking thread to stop...");
        // 设置中断信号量
        thread.stop = true;
        Thread.sleep(3000);
        System.out.println("Stopping application...");
    }
    public void run() {
        // 每隔一秒检测一下中断信号量
        while (!stop) {
            System.out.println("Thread is running...");
            long time = System.currentTimeMillis();
            /*
             * 使用while循环模拟 sleep 方法，这里不要使用sleep，否则在阻塞时会 抛
             * InterruptedException异常而退出循环，这样while检测stop条件就不会执行，
             * 失去了意义。
             */
            while ((System.currentTimeMillis() - time < 1000)) {}
        }
        System.out.println("Thread exiting under request...");
    }
}

class Example2 extends Thread {
    public static void main(String args[]) throws Exception {
        Example2 thread = new Example2();
        System.out.println("Starting thread...");
        thread.start();
        Thread.sleep(3000);
        System.out.println("Asking thread to stop...");
        // 发出中断请求
        thread.interrupt();
        Thread.sleep(3000);
        System.out.println("Stopping application...");
    }
    public void run() {
        // 每隔一秒检测是否设置了中断标示
        while (!Thread.currentThread().isInterrupted()) {
            System.out.println("Thread is running...");
            long time = System.currentTimeMillis();
            // 使用while循环模拟 sleep
            while ((System.currentTimeMillis() - time < 1000) ) {
            }
        }
        System.out.println("Thread exiting under request...");
    }
}

class Example3 extends Thread {
    public static void main(String args[]) throws Exception {
        Example3 thread = new Example3();
        System.out.println("Starting thread...");
        thread.start();
        Thread.sleep(3000);
        System.out.println("Asking thread to stop...");
        thread.interrupt();// 等中断信号量设置后再调用
        Thread.sleep(3000);
        System.out.println("Stopping application...");
    }
    public void run() {
        while (!Thread.currentThread().isInterrupted()) {
            System.out.println("Thread running...");
            try {
                /*
                 * 如果线程阻塞，将不会去检查中断信号量stop变量，所 以thread.interrupt()
                 * 会使阻塞线程从阻塞的地方抛出异常，让阻塞线程从阻塞状态逃离出来，并
                 * 进行异常块进行 相应的处理
                 */
                Thread.sleep(1000);// 线程阻塞，如果线程收到中断操作信号将抛出异常
            } catch (InterruptedException e) {
                System.out.println("Thread interrupted...");
                /*
                 * 如果线程在调用 Object.wait()方法，或者该类的 join() 、sleep()方法
                 * 过程中受阻，则其中断状态将被清除
                 */
                System.out.println(this.isInterrupted());// false
                //中不中断由自己决定，如果需要真真中断线程，则需要重新设置中断位，如果
                //不需要，则不用调用
                Thread.currentThread().interrupt();
            }
        }
        System.out.println("Thread exiting under request...");
    }
}

class Example4 extends Thread {
    public static void main(String args[]) throws Exception {
        final Object lock1 = new Object();
        final Object lock2 = new Object();
        Thread thread1 = new Thread() {
            public void run() {
                deathLock(lock1, lock2);
            }
        };
        Thread thread2 = new Thread() {
            public void run() {
                // 注意，这里在交换了一下位置
                deathLock(lock2, lock1);
            }
        };
        System.out.println("Starting thread...");
        thread1.start();
        thread2.start();
        Thread.sleep(3000);
        System.out.println("Interrupting thread...");
        thread1.interrupt();
        thread2.interrupt();
        Thread.sleep(3000);
        System.out.println("Stopping application...");
    }
    static void deathLock(Object lock1, Object lock2) {
        try {
            synchronized (lock1) {
                Thread.sleep(10);// 不会在这里死掉
                synchronized (lock2) {// 会锁在这里，虽然阻塞了，但不会抛异常
                    System.out.println(Thread.currentThread());
                }
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }
}

class Example6 extends Thread {
    volatile ServerSocket socket;
    public static void main(String args[]) throws Exception {
        Example6 thread = new Example6();
        System.out.println("Starting thread...");
        thread.start();
        Thread.sleep(3000);
        System.out.println("Asking thread to stop...");
        Thread.currentThread().interrupt();// 再调用interrupt方法
        thread.socket.close();// 再调用close方法
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
        }
        System.out.println("Stopping application...");
    }
    public void run() {
        try {
            socket = new ServerSocket(8888);
        } catch (IOException e) {
            System.out.println("Could not create the socket...");
            return;
        }
        while (!Thread.currentThread().isInterrupted()) {
            System.out.println("Waiting for connection...");
            try {
                socket.accept();
            } catch (IOException e) {
                System.out.println("accept() failed or interrupted...");
                Thread.currentThread().interrupt();//重新设置中断标示位
            }
        }
        System.out.println("Thread exiting under request...");
    }
}

#include "jni.h"
#include "jvm.h"
#include "java_lang_Thread.h"
#define THD "Ljava/lang/Thread;"
#define OBJ "Ljava/lang/Object;"
#define STE "Ljava/lang/StackTraceElement;"
#define ARRAY_LENGTH(a) (sizeof(a)/sizeof(a[0]))
static JNINativeMethod methods[] = {
    {"start0",           "()V",        (void *)&JVM_StartThread},
    {"stop0",            "(" OBJ ")V", (void *)&JVM_StopThread},
    {"isAlive",          "()Z",        (void *)&JVM_IsThreadAlive},
    {"suspend0",         "()V",        (void *)&JVM_SuspendThread},
    {"resume0",          "()V",        (void *)&JVM_ResumeThread},
    {"setPriority0",     "(I)V",       (void *)&JVM_SetThreadPriority},
    {"yield",            "()V",        (void *)&JVM_Yield},
    {"sleep",            "(J)V",       (void *)&JVM_Sleep},
    {"currentThread",    "()" THD,     (void *)&JVM_CurrentThread},
    {"countStackFrames", "()I",        (void *)&JVM_CountStackFrames},
    {"interrupt0",       "()V",        (void *)&JVM_Interrupt},
    {"isInterrupted",    "(Z)Z",       (void *)&JVM_IsInterrupted},
    {"holdsLock",        "(" OBJ ")Z", (void *)&JVM_HoldsLock},
    {"getThreads",        "()[" THD,   (void *)&JVM_GetAllThreads},
    {"dumpThreads",      "([" THD ")[[" STE, (void *)&JVM_DumpThreads},
};
#undef THD
#undef OBJ
#undef STE
JNIEXPORT void JNICALL
Java_java_lang_Thread_registerNatives(JNIEnv *env, jclass cls)
{
    (*env)->RegisterNatives(env, cls, methods, ARRAY_LENGTH(methods));
}