1.5sleep()方法

方法sleep()的作用是指在指定的毫秒数内让当前正在执行的线程休眠（暂停执行）这个正在执行的线程是指this.currentThread()返回的线程。

测试如下

package com.cky.thread;

/**
 * Created by edison on 2017/11/28.
 */
public class MyThread10 extends  Thread{
    @Override
    public void run() {
        try {
            super.run();
            System.out.println("run threadname "+this.currentThread().getName()+" begin");
            Thread.sleep(2000);
            System.out.println("run threadname "+this.currentThread().getName()+" end");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

package com.cky.test;

import com.cky.thread.MyThread10;

/**
 * Created by edison on 2017/11/28.
 */
public class Test16 {
    public static void main(String[] args) {
        MyThread10 th = new MyThread10();
        System.out.println("begin="+System.currentTimeMillis());
        th.run();
        System.out.println("end=  "+System.currentTimeMillis());
    }
}

C:itsoftjdkinjava -Didea.launcher.port=7541 "-Didea.launcher.bin.path=C:itsoftideaIntelliJ IDEA 2016.3.3in" -Dfile.encoding=UTF-8 -classpath "C:itsoftjdkjrelibcharsets.jar;C:itsoftjdkjrelibdeploy.jar;C:itsoftjdkjrelibextaccess-bridge-32.jar;C:itsoftjdkjrelibextcldrdata.jar;C:itsoftjdkjrelibextdnsns.jar;C:itsoftjdkjrelibextjaccess.jar;C:itsoftjdkjrelibextjfxrt.jar;C:itsoftjdkjrelibextlocaledata.jar;C:itsoftjdkjrelibext
ashorn.jar;C:itsoftjdkjrelibextsunec.jar;C:itsoftjdkjrelibextsunjce_provider.jar;C:itsoftjdkjrelibextsunmscapi.jar;C:itsoftjdkjrelibextsunpkcs11.jar;C:itsoftjdkjrelibextzipfs.jar;C:itsoftjdkjrelibjavaws.jar;C:itsoftjdkjrelibjce.jar;C:itsoftjdkjrelibjfr.jar;C:itsoftjdkjrelibjfxswt.jar;C:itsoftjdkjrelibjsse.jar;C:itsoftjdkjrelibmanagement-agent.jar;C:itsoftjdkjrelibplugin.jar;C:itsoftjdkjrelib
esources.jar;C:itsoftjdkjrelib
t.jar;C:多线程核心技术第一章outproduction第一章;C:itsoftideaIntelliJ IDEA 2016.3.3libidea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test16
begin=1512280757440
run threadname main begin
run threadname main end
end=  1512280759446

Process finished with exit code 0

结果分析：

直接调用run方法，说明此时并没有开启子线程，run函数里的方法都是主线程调用的，所以当线程睡眠也是主线程睡眠，代码顺序依次执行，中间最后输出的开始和结束时间相隔在2秒多的样子。

这时将调用run改成start();

package com.cky.test;

import com.cky.thread.MyThread10;

/**
 * Created by edison on 2017/11/28.
 */
public class Test16 {
    public static void main(String[] args) {
        MyThread10 th = new MyThread10();
        System.out.println("begin="+System.currentTimeMillis());
        th.start();
        System.out.println("end=  "+System.currentTimeMillis());
    }
}

C:itsoftjdkinjava -Didea.launcher.port=7540 "-Didea.launcher.bin.path=C:itsoftideaIntelliJ IDEA 2016.3.3in" -Dfile.encoding=UTF-8 -classpath "C:itsoftjdkjrelibcharsets.jar;C:itsoftjdkjrelibdeploy.jar;C:itsoftjdkjrelibextaccess-bridge-32.jar;C:itsoftjdkjrelibextcldrdata.jar;C:itsoftjdkjrelibextdnsns.jar;C:itsoftjdkjrelibextjaccess.jar;C:itsoftjdkjrelibextjfxrt.jar;C:itsoftjdkjrelibextlocaledata.jar;C:itsoftjdkjrelibext
ashorn.jar;C:itsoftjdkjrelibextsunec.jar;C:itsoftjdkjrelibextsunjce_provider.jar;C:itsoftjdkjrelibextsunmscapi.jar;C:itsoftjdkjrelibextsunpkcs11.jar;C:itsoftjdkjrelibextzipfs.jar;C:itsoftjdkjrelibjavaws.jar;C:itsoftjdkjrelibjce.jar;C:itsoftjdkjrelibjfr.jar;C:itsoftjdkjrelibjfxswt.jar;C:itsoftjdkjrelibjsse.jar;C:itsoftjdkjrelibmanagement-agent.jar;C:itsoftjdkjrelibplugin.jar;C:itsoftjdkjrelib
esources.jar;C:itsoftjdkjrelib
t.jar;C:多线程核心技术第一章outproduction第一章;C:itsoftideaIntelliJ IDEA 2016.3.3libidea_rt.jar" com.intellij.rt.execution.application.AppMain com.cky.test.Test16
begin=1512281012995
end=  1512281012995
run threadname Thread-0 begin
run threadname Thread-0 end

Process finished with exit code 0

结果分析：

使用start()方法启动线程，由于这是cpu还是切换到了主线程，main线程与子线程是异步执行的，所以，执行完了main线程，这时再执行子线程。