Java await wait sleep yield

Java併發:await/waitsleepyield間的區別java

是否釋放鎖:調用sleepyield的時候不釋放當前線程所得到的鎖,可是調用await/wait的時候卻釋放了其獲取的鎖並阻塞等待。併發

 

調用後什麼時候恢復:ide

# sleep讓線程阻塞,且在指定的時間以內都不會執行,時間到了以後恢復到就緒狀態,也不必定被當即調度執行;spa

# yield只是讓當前對象回到就緒狀態,仍是有可能立刻被再次被調用執行。線程

# await/wait,它會一直阻塞在條件隊列之上,以後某個線程調用對應的notify/signal方法,纔會使得await/wait的線程回到就緒狀態,也是不必定當即執行。對象

 

誰的方法:yieldsleep方法都是Thread類的,而wait方法是Object類的,await方法是Condition顯示條件隊列的。隊列

 

執行環境:yieldsleep方法能夠放在線程中的任意位置,而await/wait方法必須放在同步塊裏面,不然會產生運行時異常。ci


await/wait同步

Sleepit

Yield

是否釋放持有的鎖

釋放

不釋放

不釋放

調用後什麼時候恢復

喚醒後進入就緒態

指定時間後

馬上進入就緒態

誰的方法

Condition/Object

Thread

Thread

執行環境

同步代碼塊

任意位置

任意位置

 

實驗

/**

 *

 */

package com.b510.test;

/**

 *java中的sleep()wait()的區別

 *@author Hongten

 *@date 2013-12-10

 */

public class TestD {

   public static void main(String[] args) {

       new Thread(new Thread1()).start();

       try {

           Thread.sleep(5000);

       } catch (Exception e) {

           e.printStackTrace();

       }

       new Thread(new Thread2()).start();

    }

   

   private static class Thread1 implements Runnable{

       @Override

       public void run(){

           synchronized (TestD.class) {

           System.out.println("enter thread1...");   

           System.out.println("thread1 is waiting...");

           try {

                //調用wait()方法,線程會放棄對象鎖,進入等待此對象的等待鎖定池

                TestD.class.wait();

           } catch (Exception e) {

                e.printStackTrace();

           }

           System.out.println("thread1 is going on ....");

           System.out.println("thread1 is over!!!");

           }

       }

    }

   

   private static class Thread2 implements Runnable{

       @Override

       public void run(){

           synchronized (TestD.class) {

                System.out.println("enterthread2....");

               System.out.println("thread2 is sleep....");

                //只有針對此對象調用notify()方法後本線程才進入對象鎖定池準備獲取對象鎖進入運行狀態。

                TestD.class.notify();

                //==================

                //區別

                //若是咱們把代碼:TestD.class.notify();給註釋掉,即TestD.class調用了wait()方法,可是沒有調用notify()

                //方法,則線程永遠處於掛起狀態。

                try {

                    //sleep()方法致使了程序暫停執行指定的時間,讓出cpu該其餘線程,

                    //可是他的監控狀態依然保持者,當指定的時間到了又會自動恢復運行狀態。

                    //在調用sleep()方法的過程當中,線程不會釋放對象鎖。

                    Thread.sleep(5000);

                } catch (Exception e) {

                    e.printStackTrace();

                }

               System.out.println("thread2 isgoing on....");

               System.out.println("thread2 is over!!!");

           }

       }

    }

}

運行效果:

enter thread1...

thread1 is waiting...

enter thread2....

thread2 is sleep....

thread2 is going on....

thread2 is over!!!

thread1 is going on ....

thread1 is over!!!

若是註釋掉代碼:

TestD.class.notify();

運行效果:

enter thread1...

thread1 is waiting...

enter thread2....

thread2 is sleep....

thread2 is going on....

thread2 is over!!!

且程序一直處於掛起狀態。

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