多线程那些事（二）

今天我们来讨论一下，同一个类中的多个方法都加了同步锁，多个线程能同时访问同一个类中的这两个方法吗？

第一种情况：使用synchronized关键字

/**
 * @program:
 * 使用 synchronized 时，当我们访问同一个类对象的时候，是同一把锁，所以可以访问 该对象的其他 synchronized 方法
 * @description: ${description}
 * @author: Will Wu
 * @create: 2018-12-09 10:09
 **/
@Slf4j
public class MultiThreadO {
    private int count=0;
    private Lock lock=new ReentrantLock();
    public Runnable runnableone=new Runnable() {
        @Override
        public void run() {
            //设置关键字synchronized,以当前类为锁
            synchronized (this){
                while (count<100){
                    log.info(Thread.currentThread().getName()+"run 1:"+count++);
                }
            }
        }
    };

    public Runnable runnabletwo=new Runnable() {
        @Override
        public void run() {
            synchronized (this){
                while (count<100){
                    log.info(Thread.currentThread().getName()+"run 2:"+count++);
                }
            }
        }
    };

    public static void main(String[] args) {
        MultiThreadO multiThread = new MultiThreadO();
        new Thread(multiThread.runnableone).start();
        new Thread(multiThread.runnabletwo).start();

    }

}

运行结果如下：

/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/bin/java -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/lib/tools.jar:/Users/wuyundong/IdeaProjects/demo/target/classes:/Users/wuyundong/.m2/repository/org/springframework/boot/spring-boot-starter/2.1.1.RELEASE/spring-boot-starter-2.1.1.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/boot/spring-boot/2.1.1.RELEASE/spring-boot-2.1.1.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/spring-context/5.1.3.RELEASE/spring-context-5.1.3.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/spring-aop/5.1.3.RELEASE/spring-aop-5.1.3.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/spring-beans/5.1.3.RELEASE/spring-beans-5.1.3.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/spring-expression/5.1.3.RELEASE/spring-expression-5.1.3.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.1.1.RELEASE/spring-boot-autoconfigure-2.1.1.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.1.1.RELEASE/spring-boot-starter-logging-2.1.1.RELEASE.jar:/Users/wuyundong/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/Users/wuyundong/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/Users/wuyundong/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.11.1/log4j-to-slf4j-2.11.1.jar:/Users/wuyundong/.m2/repository/org/apache/logging/log4j/log4j-api/2.11.1/log4j-api-2.11.1.jar:/Users/wuyundong/.m2/repository/org/slf4j/jul-to-slf4j/1.7.25/jul-to-slf4j-1.7.25.jar:/Users/wuyundong/.m2/repository/javax/annotation/javax.annotation-api/1.3.2/javax.annotation-api-1.3.2.jar:/Users/wuyundong/.m2/repository/org/springframework/spring-core/5.1.3.RELEASE/spring-core-5.1.3.RELEASE.jar:/Users/wuyundong/.m2/repository/org/springframework/spring-jcl/5.1.3.RELEASE/spring-jcl-5.1.3.RELEASE.jar:/Users/wuyundong/.m2/repository/org/yaml/snakeyaml/1.23/snakeyaml-1.23.jar:/Users/wuyundong/.m2/repository/org/projectlombok/lombok/1.18.4/lombok-1.18.4.jar:/Users/wuyundong/.m2/repository/org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar com.example.demo.thread.MultiThreadO
10:22:04.589 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:0
10:22:04.589 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:1
10:22:04.595 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:2
10:22:04.595 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:3
10:22:04.595 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:4
10:22:04.595 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:5
10:22:04.595 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:6
10:22:04.595 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:7
10:22:04.595 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:8
10:22:04.595 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:9
10:22:04.595 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:10
10:22:04.595 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:11
10:22:04.595 [Thread-0] INFO com.example.demo.thread.MultiThreadO - Thread-0run 1:12
10:22:04.595 [Thread-1] INFO com.example.demo.thread.MultiThreadO - Thread-1run 2:13

从结果可以看到：

使用 synchronized 时，当我们访问同一个类对象的时候，是同一把锁，所以可以访问该对象的其他 synchronized 方法

第二种情况：使用lock


/**
 * @program: 多个线程不可访问同一个类中的 2 个加了 Lock 锁的方法
 * @description: ${description}
 * @author: Will Wu
 * @create: 2018-12-09 09:53
 **/
@Slf4j
public class MultiThread {

    private int count=0;
    //lock
    private Lock lock=new ReentrantLock();

    private  Runnable runnableone=new Runnable() {
        @Override
        public void run() {
            //lock
            lock.lock();
            while (count<100){
                try {
                    //是否执行该方法
                    log.info(Thread.currentThread().getName()+"run 1:"+count++);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            lock.unlock();
        }
    };

    private Runnable runnabletwo=new Runnable() {
        @Override
        public void run() {
            lock.lock();
            while(count<100){
                log.info(Thread.currentThread().getName()+"run 2:"+count++);
            }
            lock.unlock();
        }
    };


    public static void main(String[] args) {
        MultiThread qq = new MultiThread();
        new Thread(qq.runnableone).start();
        new Thread(qq.runnabletwo).start();
    }
}

执行后结果如下：

10:27:11.310 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:0
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:1
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:2
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:3
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:4
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:5
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:6
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:7
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:8
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:9
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:10
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:11
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:12
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:13
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:14
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:15
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:16
10:27:11.315 [Thread-0] INFO com.example.demo.thread.MultiThread - Thread-0run 1:17

因此：

多个线程不可访问同一个类中的 2 个加了 Lock 锁的方法；

多线程那些事（二）

今天我们来讨论一下，同一个类中的多个方法都加了同步锁，多个线程能同时访问同一个类中的这两 个方法吗？

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今天我们来讨论一下，同一个类中的多个方法都加了同步锁，多个线程能同时访问同一个类中的这两个方法吗？