2.2.1synchronized方法的弊端

缺陷：用关键字synchronized声明方法是有弊端的，譬如A线程调用同步方法执行一个长时间的任务，那么B线程则必须等待较长的时间，

解决方法：使用synchronized同步语句块

 package com.cky.utils;
 
 /**
  * Created by chenkaiyang on 2017/12/6.
  */
 public class Task {
     private String getData1;
     private String getData2;
     public synchronized  void doLongTimeTask() {
         try {
             System.out.println("begin task");
             Thread.sleep();
             getData1 = "长时间处理任务后从远程返回的值 1 ThreadName="+ Thread.currentThread().getName();
             getData2 = "长时间处理任务后从远程返回的值 2 ThreadName="+ Thread.currentThread().getName();
             System.out.println(getData1);
             System.out.println(getData2);
             System.out.println("end");
         } catch (InterruptedException e) {
             e.printStackTrace();
         }
     }
 }

package com.cky.utils;
 
/**
 * Created by chenkaiyang on 2017/12/6.
 */
public class CommonUtils {
    public static long beginTime1;
    public static long endTime1;
    public static long beginTime2;
    public static long endTime2;
}

package com.cky.thread;
 
import com.cky.utils.CommonUtils;
import com.cky.utils.Task;
 
/**
 * Created by chenkaiyang on 2017/12/6.
 */
public class MyThreadA extends  Thread{
    private Task task;
    public MyThreadA (Task task) {
        this.task = task;
    }
    @Override
    public void run() {
        super.run();
        CommonUtils.beginTime1 = System.currentTimeMillis();
        task.doLongTimeTask();
        CommonUtils.endTime1 = System.currentTimeMillis();
    }
}

package com.cky.thread;
 
import com.cky.utils.CommonUtils;
import com.cky.utils.Task;
 
/**
 * Created by chenkaiyang on 2017/12/6.
 */
public class MyThreadB extends Thread{
    private Task task;
    public MyThreadB (Task task) {
        this.task = task;
    }
    @Override
    public void run() {
        super.run();
        CommonUtils.beginTime2 = System.currentTimeMillis();
        task.doLongTimeTask();
        CommonUtils.endTime2 = System.currentTimeMillis();
    }
}

package com.cky.test;
 
import com.cky.thread.MyThreadA;
import com.cky.thread.MyThreadB;
import com.cky.utils.CommonUtils;
import com.cky.utils.Task;
 
/**
 * Created by chenkaiyang on 2017/12/2.
 */
public class Test {
    public static void main(String[] args){
        Task task = new Task();
        MyThreadA myThreadA = new MyThreadA(task);
        myThreadA.start();
        MyThreadB myThreadB = new MyThreadB(task);
        myThreadB.start();
        try {
            Thread.sleep();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        long beginTime = (CommonUtils.beginTime2 <CommonUtils.beginTime1?CommonUtils.beginTime2:CommonUtils.beginTime1);
        long endTime = (CommonUtils.endTime2> CommonUtils.endTime1?CommonUtils.endTime2:CommonUtils.endTime1);
        System.out.println("耗时"+ (endTime- beginTime)/);
 
    }
}

D:\it\jdk1.\bin\java -Didea.launcher.port= "-Didea.launcher.bin.path=D:\it\idea\IntelliJ IDEA 2016.3.3\bin" -Dfile.encoding=UTF- -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 task
长时间处理任务后从远程返回的值  ThreadName=Thread-
长时间处理任务后从远程返回的值  ThreadName=Thread-
end
begin task
长时间处理任务后从远程返回的值  ThreadName=Thread-
长时间处理任务后从远程返回的值  ThreadName=Thread-
end
耗时6

程序运行了大约6秒。

需要使用同步代码块来解决。