多线程之8锁问题

Phone 有两个方法：发送邮件和发送短信，每个方法都打印一句话，现在通过不同的方式对方法进行操作，回答出打印的先后顺序（建议先自己看代码认真思考，然后再看答案，文章结尾会对每个问题进行分析）

问题

1、标准访问，两线程中间睡眠 2 毫秒，先打印邮件还是短信？

class Phone { public synchronized void sendEmail() { System.out.println("send email"); } public synchronized void sendSms() { System.out.println("send sms"); } } public class Lock01 { public static void main(String[] args) throws InterruptedException { Phone phone = new Phone(); new Thread(() -> phone.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone.sendSms(), "B").start(); } } 查看答案 send email
send sms

2、在 sendEmail() 方法中睡眠 4 秒，先打印邮件还是短信？

class Phone { public synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public synchronized void sendSms() { System.out.println("send sms"); } } public class Lock02 { public static void main(String[] args) throws InterruptedException { Phone phone = new Phone(); new Thread(() -> phone.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone.sendSms(), "B").start(); } } 查看答案 send email
send sms

3、添加普通的 hello() 方法，先打印邮件还是 hello？

class Phone { public synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public void hello() { System.out.println("hello"); } } public class Lock03 { public static void main(String[] args) throws InterruptedException { Phone phone = new Phone(); new Thread(() -> phone.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone.hello(), "B").start(); } } 查看答案 hello
send email

4、2 个手机，先打印邮件还是短信？

class Phone { public synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public synchronized void sendSms() { System.out.println("send sms"); } } public class Lock04 { public static void main(String[] args) throws InterruptedException { Phone phone1 = new Phone(); Phone phone2 = new Phone(); new Thread(() -> phone1.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone2.sendSms(), "B").start(); } } 查看答案 send sms
send email

5、2个静态同步方法，1部手机，先打印邮件还是短信？

class Phone { public static synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public static synchronized void sendSms() { System.out.println("send sms"); } } public class Lock05 { public static void main(String[] args) throws InterruptedException { Phone phone = new Phone(); new Thread(() -> phone.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone.sendSms(), "B").start(); } } 查看答案 send email
send sms **6、2个静态同步方法，2部手机，先打印邮件还是短信？** class Phone { public static synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public static synchronized void sendSms() { System.out.println("send sms"); } } public class Lock06 { public static void main(String[] args) throws InterruptedException { Phone phone1 = new Phone(); Phone phone2 = new Phone(); new Thread(() -> phone1.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone2.sendSms(), "B").start(); } } 查看答案 send email
send sms **7、1个静态同步方法，1个普通同步方法，1部手机，先打印邮件还是短信？** class Phone { public static synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public synchronized void sendSms() { System.out.println("send sms"); } } public class Lock07 { public static void main(String[] args) throws InterruptedException { Phone phone = new Phone(); new Thread(() -> phone.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone.sendSms(), "B").start(); } } 查看答案 send sms
send email

8、1个静态同步方法，1个普通同步方法，2部手机，先打印邮件还是短信？

class Phone { public static synchronized void sendEmail() { try { Thread.sleep(4000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("send email"); } public synchronized void sendSms() { System.out.println("send sms"); } } public class Lock08 { public static void main(String[] args) throws InterruptedException { Phone phone1 = new Phone(); Phone phone2 = new Phone(); new Thread(() -> phone1.sendEmail(), "A").start(); Thread.sleep(200); new Thread(() -> phone2.sendSms(), "B").start(); } } 查看答案 send sms
send email 分析