2.1.6synchronized锁重入

关键字在使用synchronized时，当线程得到一个对象锁时，这时这个线程再次请求此对象锁是可以拿到的，也就说明同步方法之间是可以进行互相调用的，

package com.cky.bean;

/**
 * Created by chenkaiyang on 2017/12/5.
 */
public class Service {
   synchronized public void service1() {
        System.out.println("service1");
        service2();
    }

    synchronized public void service2() {
        System.out.println("service2");
        service3();
    }

    synchronized public void service3() {
        System.out.println("service3");
    }
}

package com.cky.thread;

import com.cky.bean.Service;

/**
 * Created by chenkaiyang on 2017/12/5.
 */
public class MyThread extends Thread{
    @Override
    public void run() {
        super.run();
        Service service = new Service();
        service.service1();
    }
}

package com.cky.test;

import com.cky.thread.MyThread;

/**
 * Created by chenkaiyang on 2017/12/2.
 */
public class Test {
    public static void main(String[] args){
        MyThread myThread = new MyThread();
        myThread.start();

    }
}

D:itjdk1.8injava -Didea.launcher.port=7532 "-Didea.launcher.bin.path=D:itideaIntelliJ IDEA 2016.3.3in" -Dfile.encoding=UTF-8 -classpath "D:itjdk1.8jrelibcharsets.jar;D:itjdk1.8jrelibdeploy.jar;D:itjdk1.8jrelibextaccess-bridge-64.jar;D:itjdk1.8jrelibextcldrdata.jar;D:itjdk1.8jrelibextdnsns.jar;D:itjdk1.8jrelibextjaccess.jar;D:itjdk1.8jrelibextjfxrt.jar;D:itjdk1.8jrelibextlocaledata.jar;D:itjdk1.8jrelibext
ashorn.jar;D:itjdk1.8jrelibextsunec.jar;D:itjdk1.8jrelibextsunjce_provider.jar;D:itjdk1.8jrelibextsunmscapi.jar;D:itjdk1.8jrelibextsunpkcs11.jar;D:itjdk1.8jrelibextzipfs.jar;D:itjdk1.8jrelibjavaws.jar;D:itjdk1.8jrelibjce.jar;D:itjdk1.8jrelibjfr.jar;D:itjdk1.8jrelibjfxswt.jar;D:itjdk1.8jrelibjsse.jar;D:itjdk1.8jrelibmanagement-agent.jar;D:itjdk1.8jrelibplugin.jar;D:itjdk1.8jrelib
esources.jar;D:itjdk1.8jrelib
t.jar;F:springboot	hreaddemooutproduction	hreaddemo;D:itideaIntelliJ IDEA 2016.3.3libidea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test
service1
service2
service3

Process finished with exit code 0

可重入锁的概念：

自己可以再次获取自己的内部锁，譬如有一条线程获得了某个对象的对象锁，此时这个对象锁还没释放，当其要再次获得这个对象锁的时候还能获取，如果不能获取，则会造成死锁。

package com.cky.bean;

/**
 * Created by chenkaiyang on 2017/12/5.
 */
public class Father {
    public int i=10;
    synchronized public void opeFatherMethod() {
        try {
            i--;
            System.out.println("main print i=" + i);
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

package com.cky.bean;

/**
 * Created by chenkaiyang on 2017/12/5.
 */
public class Son extends  Father{
    synchronized  public void opereSonMethod(){
        try {
            while(i > 0) {
                i--;
                System.out.println("sub print i="+i);
                Thread.sleep(2000);
                this.opeFatherMethod();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

package com.cky.thread;

import com.cky.bean.Son;

/**
 * Created by chenkaiyang on 2017/12/5.
 */
public class MyThread extends Thread{
    @Override
    public void run() {
        super.run();
        Son service = new Son();
        service.opereSonMethod();
    }
}

package com.cky.test;

import com.cky.thread.MyThread;

/**
 * Created by chenkaiyang on 2017/12/2.
 */
public class Test {
    public static void main(String[] args){
        MyThread myThread = new MyThread();
        myThread.start();

    }
}

D:itjdk1.8injava -Didea.launcher.port=7536 "-Didea.launcher.bin.path=D:itideaIntelliJ IDEA 2016.3.3in" -Dfile.encoding=UTF-8 -classpath "D:itjdk1.8jrelibcharsets.jar;D:itjdk1.8jrelibdeploy.jar;D:itjdk1.8jrelibextaccess-bridge-64.jar;D:itjdk1.8jrelibextcldrdata.jar;D:itjdk1.8jrelibextdnsns.jar;D:itjdk1.8jrelibextjaccess.jar;D:itjdk1.8jrelibextjfxrt.jar;D:itjdk1.8jrelibextlocaledata.jar;D:itjdk1.8jrelibext
ashorn.jar;D:itjdk1.8jrelibextsunec.jar;D:itjdk1.8jrelibextsunjce_provider.jar;D:itjdk1.8jrelibextsunmscapi.jar;D:itjdk1.8jrelibextsunpkcs11.jar;D:itjdk1.8jrelibextzipfs.jar;D:itjdk1.8jrelibjavaws.jar;D:itjdk1.8jrelibjce.jar;D:itjdk1.8jrelibjfr.jar;D:itjdk1.8jrelibjfxswt.jar;D:itjdk1.8jrelibjsse.jar;D:itjdk1.8jrelibmanagement-agent.jar;D:itjdk1.8jrelibplugin.jar;D:itjdk1.8jrelib
esources.jar;D:itjdk1.8jrelib
t.jar;F:springboot	hreaddemooutproduction	hreaddemo;D:itideaIntelliJ IDEA 2016.3.3libidea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test
sub print i=9
main print i=8
sub print i=7
main print i=6
sub print i=5
main print i=4
sub print i=3
main print i=2
sub print i=1
main print i=0

Process finished with exit code 0

结果说明：当存在父子类继承关系时，子类完全可以通过可重入锁调用父类同步方法