2.1.4synchronized方法与锁对象

为了证明线程锁的是对象

测试

 package com.cky.bean;

 /**

  * Created by chenkaiyang on 2017/12/4.

  */

 public class MyObject {

     public void methodA () {

         try {

             System.out.println("begin methodA ThName=" +Thread.currentThread().getName());

             Thread.sleep(5000);

             System.out.println("end");

         } catch (InterruptedException e) {

             e.printStackTrace();

         }

     }

 }

 package com.cky.thread;

 import com.cky.bean.MyObject;

 /**

  * Created by chenkaiyang on 2017/12/4.

  */

 public class ThreadA  extends Thread{

     private MyObject mo;

     public ThreadA (MyObject mo) {

         this.mo = mo;

     }

     @Override

     public void run() {

         super.run();

         mo.methodA();

     }

 }

package com.cky.thread;

import com.cky.bean.MyObject;

/**

 * Created by chenkaiyang on 2017/12/4.

 */

public class ThreadB extends Thread{

    private MyObject mo;

    public ThreadB (MyObject mo) {

        this.mo = mo;

    }

    @Override

    public void run() {

        super.run();

        mo.methodA();

    }

}

package com.cky.test;

import com.cky.bean.MyObject;

import com.cky.thread.ThreadA;

import com.cky.thread.ThreadB;

/**

 * Created by chenkaiyang on 2017/12/2.

 */

public class Test {

    public static void main(String[] args){

        MyObject myObject = new MyObject();

        ThreadA threadA = new ThreadA(myObject);

        threadA.setName("A");

        ThreadB threadB = new ThreadB(myObject);

        threadB.setName("B");

        threadA.start();

        threadB.start();

    }

}

D:\it\jdk1.8\bin\java -Didea.launcher.port=7533 "-Didea.launcher.bin.path=D:\it\idea\IntelliJ IDEA 2016.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\it\jdk1.8\jre\lib\charsets.jar;D:\it\jdk1.8\jre\lib\deploy.jar;D:\it\jdk1.8\jre\lib\ext\access-bridge-64.jar;D:\it\jdk1.8\jre\lib\ext\cldrdata.jar;D:\it\jdk1.8\jre\lib\ext\dnsns.jar;D:\it\jdk1.8\jre\lib\ext\jaccess.jar;D:\it\jdk1.8\jre\lib\ext\jfxrt.jar;D:\it\jdk1.8\jre\lib\ext\localedata.jar;D:\it\jdk1.8\jre\lib\ext\nashorn.jar;D:\it\jdk1.8\jre\lib\ext\sunec.jar;D:\it\jdk1.8\jre\lib\ext\sunjce_provider.jar;D:\it\jdk1.8\jre\lib\ext\sunmscapi.jar;D:\it\jdk1.8\jre\lib\ext\sunpkcs11.jar;D:\it\jdk1.8\jre\lib\ext\zipfs.jar;D:\it\jdk1.8\jre\lib\javaws.jar;D:\it\jdk1.8\jre\lib\jce.jar;D:\it\jdk1.8\jre\lib\jfr.jar;D:\it\jdk1.8\jre\lib\jfxswt.jar;D:\it\jdk1.8\jre\lib\jsse.jar;D:\it\jdk1.8\jre\lib\management-agent.jar;D:\it\jdk1.8\jre\lib\plugin.jar;D:\it\jdk1.8\jre\lib\resources.jar;D:\it\jdk1.8\jre\lib\rt.jar;F:\springboot\threaddemo\out\production\threaddemo;D:\it\idea\IntelliJ IDEA 2016.3.3\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test

begin methodA ThName=A

begin methodA ThName=B

end

end

结果如上分析，代码调用是异步随机执行。

然后在方法中加同步关键字

package com.cky.bean;

/**

 * Created by chenkaiyang on 2017/12/4.

 */

public class MyObject {

    synchronized  public void methodA () {

        try {

            System.out.println("begin methodA ThName=" +Thread.currentThread().getName());

            Thread.sleep(5000);

            System.out.println("end");

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}

D:\it\jdk1.8\bin\java -Didea.launcher.port=7534 "-Didea.launcher.bin.path=D:\it\idea\IntelliJ IDEA 2016.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\it\jdk1.8\jre\lib\charsets.jar;D:\it\jdk1.8\jre\lib\deploy.jar;D:\it\jdk1.8\jre\lib\ext\access-bridge-64.jar;D:\it\jdk1.8\jre\lib\ext\cldrdata.jar;D:\it\jdk1.8\jre\lib\ext\dnsns.jar;D:\it\jdk1.8\jre\lib\ext\jaccess.jar;D:\it\jdk1.8\jre\lib\ext\jfxrt.jar;D:\it\jdk1.8\jre\lib\ext\localedata.jar;D:\it\jdk1.8\jre\lib\ext\nashorn.jar;D:\it\jdk1.8\jre\lib\ext\sunec.jar;D:\it\jdk1.8\jre\lib\ext\sunjce_provider.jar;D:\it\jdk1.8\jre\lib\ext\sunmscapi.jar;D:\it\jdk1.8\jre\lib\ext\sunpkcs11.jar;D:\it\jdk1.8\jre\lib\ext\zipfs.jar;D:\it\jdk1.8\jre\lib\javaws.jar;D:\it\jdk1.8\jre\lib\jce.jar;D:\it\jdk1.8\jre\lib\jfr.jar;D:\it\jdk1.8\jre\lib\jfxswt.jar;D:\it\jdk1.8\jre\lib\jsse.jar;D:\it\jdk1.8\jre\lib\management-agent.jar;D:\it\jdk1.8\jre\lib\plugin.jar;D:\it\jdk1.8\jre\lib\resources.jar;D:\it\jdk1.8\jre\lib\rt.jar;F:\springboot\threaddemo\out\production\threaddemo;D:\it\idea\IntelliJ IDEA 2016.3.3\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test

begin methodA ThName=A

end

begin methodA ThName=B

end

结果分析：

调用关键字synchronized声明的方法一定是排队运行的，只有共享的资源才需要同步，如果不是共享的资源，根本没有必要同步。

那如果其他的方法被调用会有什么效果。

测试

继续更改MyObject

package com.cky.bean;

/**

 * Created by chenkaiyang on 2017/12/4.

 */

public class MyObject {

    synchronized  public void methodA () {

        try {

            System.out.println("begin methodA ThName=" +Thread.currentThread().getName());

            Thread.sleep(5000);

            System.out.println("end");

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

    public void methodB() {

        try {

            System.out.println("begin methodB ThName=" +Thread.currentThread().getName());

            Thread.sleep(5000);

            System.out.println("end");

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}

package com.cky.thread;

import com.cky.bean.MyObject;

/**

 * Created by chenkaiyang on 2017/12/4.

 */

public class ThreadA  extends Thread{

    private MyObject mo;

    public ThreadA (MyObject mo) {

        this.mo = mo;

    }

    @Override

    public void run() {

        super.run();

        mo.methodA();

    }

}

package com.cky.thread;

import com.cky.bean.MyObject;

/**

 * Created by chenkaiyang on 2017/12/4.

 */

public class ThreadB extends Thread{

    private MyObject mo;

    public ThreadB (MyObject mo) {

        this.mo = mo;

    }

    @Override

    public void run() {

        super.run();

        mo.methodB();

    }

}

package com.cky.test;

import com.cky.bean.MyObject;

import com.cky.thread.ThreadA;

import com.cky.thread.ThreadB;

/**

 * Created by chenkaiyang on 2017/12/2.

 */

public class Test {

    public static void main(String[] args){

        MyObject myObject = new MyObject();

        ThreadA threadA = new ThreadA(myObject);

        threadA.setName("A");

        ThreadB threadB = new ThreadB(myObject);

        threadB.setName("B");

        threadA.start();

        threadB.start();

    }

}

D:\it\jdk1.8\bin\java -Didea.launcher.port=7536 "-Didea.launcher.bin.path=D:\it\idea\IntelliJ IDEA 2016.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\it\jdk1.8\jre\lib\charsets.jar;D:\it\jdk1.8\jre\lib\deploy.jar;D:\it\jdk1.8\jre\lib\ext\access-bridge-64.jar;D:\it\jdk1.8\jre\lib\ext\cldrdata.jar;D:\it\jdk1.8\jre\lib\ext\dnsns.jar;D:\it\jdk1.8\jre\lib\ext\jaccess.jar;D:\it\jdk1.8\jre\lib\ext\jfxrt.jar;D:\it\jdk1.8\jre\lib\ext\localedata.jar;D:\it\jdk1.8\jre\lib\ext\nashorn.jar;D:\it\jdk1.8\jre\lib\ext\sunec.jar;D:\it\jdk1.8\jre\lib\ext\sunjce_provider.jar;D:\it\jdk1.8\jre\lib\ext\sunmscapi.jar;D:\it\jdk1.8\jre\lib\ext\sunpkcs11.jar;D:\it\jdk1.8\jre\lib\ext\zipfs.jar;D:\it\jdk1.8\jre\lib\javaws.jar;D:\it\jdk1.8\jre\lib\jce.jar;D:\it\jdk1.8\jre\lib\jfr.jar;D:\it\jdk1.8\jre\lib\jfxswt.jar;D:\it\jdk1.8\jre\lib\jsse.jar;D:\it\jdk1.8\jre\lib\management-agent.jar;D:\it\jdk1.8\jre\lib\plugin.jar;D:\it\jdk1.8\jre\lib\resources.jar;D:\it\jdk1.8\jre\lib\rt.jar;F:\springboot\threaddemo\out\production\threaddemo;D:\it\idea\IntelliJ IDEA 2016.3.3\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test

begin methodA ThName=A

begin methodB ThName=B

end

end

结果分析:虽然线程A先持有object对象的锁，但是线程B完全可以异步调用非synchronized类型的方法。

继续再methodB方法上加上synchronized

package com.cky.bean;

/**

 * Created by chenkaiyang on 2017/12/4.

 */

public class MyObject {

    synchronized  public void methodA () {

        try {

            System.out.println("begin methodA ThName=" +Thread.currentThread().getName());

            Thread.sleep(5000);

            System.out.println("end");

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

   synchronized public void methodB() {

        try {

            System.out.println("begin methodB ThName=" +Thread.currentThread().getName());

            Thread.sleep(5000);

            System.out.println("end");

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}

D:\it\jdk1.8\bin\java -Didea.launcher.port=7537 "-Didea.launcher.bin.path=D:\it\idea\IntelliJ IDEA 2016.3.3\bin" -Dfile.encoding=UTF-8 -classpath "D:\it\jdk1.8\jre\lib\charsets.jar;D:\it\jdk1.8\jre\lib\deploy.jar;D:\it\jdk1.8\jre\lib\ext\access-bridge-64.jar;D:\it\jdk1.8\jre\lib\ext\cldrdata.jar;D:\it\jdk1.8\jre\lib\ext\dnsns.jar;D:\it\jdk1.8\jre\lib\ext\jaccess.jar;D:\it\jdk1.8\jre\lib\ext\jfxrt.jar;D:\it\jdk1.8\jre\lib\ext\localedata.jar;D:\it\jdk1.8\jre\lib\ext\nashorn.jar;D:\it\jdk1.8\jre\lib\ext\sunec.jar;D:\it\jdk1.8\jre\lib\ext\sunjce_provider.jar;D:\it\jdk1.8\jre\lib\ext\sunmscapi.jar;D:\it\jdk1.8\jre\lib\ext\sunpkcs11.jar;D:\it\jdk1.8\jre\lib\ext\zipfs.jar;D:\it\jdk1.8\jre\lib\javaws.jar;D:\it\jdk1.8\jre\lib\jce.jar;D:\it\jdk1.8\jre\lib\jfr.jar;D:\it\jdk1.8\jre\lib\jfxswt.jar;D:\it\jdk1.8\jre\lib\jsse.jar;D:\it\jdk1.8\jre\lib\management-agent.jar;D:\it\jdk1.8\jre\lib\plugin.jar;D:\it\jdk1.8\jre\lib\resources.jar;D:\it\jdk1.8\jre\lib\rt.jar;F:\springboot\threaddemo\out\production\threaddemo;D:\it\idea\IntelliJ IDEA 2016.3.3\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test

begin methodB ThName=B

end

begin methodA ThName=A

end

Process finished with exit code 0

结果分析：

1）A线程先持有对象锁，B线程可以异步方法调用object对象中非同步的方法

2）A线程先持有对象锁，B线程此时如果想要调用B线程中其他的同步方法，则需要等待A线程释放才行

巴特西

2.1.4synchronized方法与锁对象

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