Java多線程二

原創 NicolasYan 2020-02-22 02:05

1. 線程的狀態回顧

  線程從創建到最終的消亡，要經歷若干個狀態。一般來說，線程包括以下這幾個狀態：（原文更好理解，就不翻譯了）

  1. New When we create a new Thread object using new operator, thread state is New Thread. At this point, thread is not alive and it’s a state internal to Java programming.
  2. Runnable When we call start() function on Thread object, it’s state is changed to Runnable and the control is given to Thread scheduler to finish it’s execution. Whether to run this thread instantly or keep it in runnable thread pool before running it depends on the OS implementation of thread scheduler.
  3. Running When thread is executing, it’s state is changed to Running. Thread scheduler picks one of the thread from the runnable thread pool and change it’s state to Running and CPU starts executing this thread. A thread can change state to Runnable, Dead or Blocked from running state depends on time slicing, thread completion of run() method or waiting for some resources like IO,Network,etc.
  4. Blocked/Waiting A thread can be waiting for other thread to finish using thread join or it can be waiting for some resources to available, for example producer consumer problem （生產者-消費者問題）or waiter notifier implementation or IO resources, then it’s state is changed to Waiting. Once the thread wait state is over, it’s state is changed to Runnable and it’s moved back to runnable thread pool.
  5. Dead Once the thread finished executing, it’s state is changed to Dead and it’s considered to be not alive.

這裏寫圖片描述

2. 線程生命週期中常用方法總結

2.1 sleep(long millis)

  運行的線程調用sleep方法進入阻塞狀態(不會釋放任何對象鎖)，睡眠完之後繼續進入就緒狀態，等待線程調度。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">sleepMethod</span>() {
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Runnable() {
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> start = System.currentTimeMillis();
                Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> end = System.currentTimeMillis();
                System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(end -start);
            } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }).start();
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

  輸出結果可能稍微大於2000ms。Thread.sleep() 和線程調度模塊交互，將當前線程設置爲阻塞狀態，等待指定的時間。一旦等待時間結束，線程的狀態切換爲可執行狀態，等待CPU的時間片輪轉。所以等待的確切時間取決於操作系統的線程調度機制和定時器的精度。 
  注意：

  1. 線程sleep期間，並沒有失去此線程所獲得的監視器(monitors)和鎖(locks)。 
  2. 線程sleep期間，任何其他的線程抖可以中斷此線程，一旦中斷，則拋出InterruptedException.

2.2 join()

  join()可以用來暫停當前線程的執行，讓調用join()的線程強制運行完成或執行指定的時間。 
public final void join() 
public final synchronized void join(long millis) 
public final synchronized void join(long millis, int nanos) 
  測試案例：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">joinMethod</span>() {
    Thread thread1 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(), <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread1"</span>);
    Thread thread2 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(), <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread2"</span>);
    Thread thread3 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(), <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread3"</span>);
    thread1.start(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//thread1啓動，此時只有thread1和main線程競爭</span>

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 等待thread1死亡，即此時main線程處於阻塞狀態</span>
        thread1.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">join</span>();
    } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
        e.printStackTrace();
    }
    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread1死亡，繼續執行..."</span>);
    thread2.start();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//thread2啓動，此時只有thread2和main線程競爭</span>

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 等待thread2執行5s或還沒執行到5s就死亡</span>
        thread2.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">join</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5000</span>);
    } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
        e.printStackTrace();
    }
    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread2已經執行了5s或已經死亡，繼續執行..."</span>);
    thread3.start();
    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"---此後線程thread2和thread3競爭執行---"</span>);
    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"main線程執行完..."</span>);
}

class MyRunnable implements Runnable{
    @Override
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
        String threadName = Thread.currentThread().getName();
        System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread started..."</span> + threadName);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>; i++) {
                Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4000</span>);
                System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"---->"</span> + threadName + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" is running..."</span>);
            }
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
            e.printStackTrace();
        }
        System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread ended..."</span> + threadName);
    }
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li></ul>

  執行thread1.join();，main線程將處於阻塞狀態，此時只有thread1執行，等待thread1執行完處於死亡狀態後，切換到main線程，同理執行thread2.join(5000);，main線程等待thread2執行5s或死亡。注意當執行thread3.start();時，由於此時的thread2並沒有執行完，所以此後是thread2、thread3以及main線程競爭。 
  運行結果： 
    這裏寫圖片描述

2.3 interrupt()

  Java中斷機制是一種協作機制，也就是說通過中斷並不能直接終止另一個線程，而需要被中斷的線程自己處理中斷。當調用interrupt()方法的時候,只是設置了要中斷線程的中斷狀態。我們可以從interrupt()方法來看：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">interrupt</span>() {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span> != Thread.currentThread())
            checkAccess();
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">synchronized</span> (blockerLock) {
            Interruptible b = blocker;
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (b != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) {
                interrupt0();           <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Just to set the interrupt flag</span>
                b.interrupt(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>;
            }
        }
        interrupt0();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Just to set the interrupt flag</span>
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

  最終調用的是interrupt0()方法，而interrupt0()只是設置了中斷標誌位，並沒有實際中斷該線程。 
  而此時被中斷的線程的可以通過isInterrupted()或interrupted()方法判斷當前線程的中斷狀態。看下isInterrupted()方法：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">   <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">isInterrupted</span>() {
       <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> isInterrupted(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>);
   }
   <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
    * Tests if some Thread has been interrupted.  The interrupted state
    * is reset or not based on the value of ClearInterrupted that is
    * passed.
    */</span>
   <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">native</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">isInterrupted</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> ClearInterrupted);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

  從這個方法可以看出：isInterrupted()方法僅僅是檢查了當前線程的中斷狀態，但是不會清除這個狀態。 
  看下interrupted()方法：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">   <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">interrupted</span>() {
       <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> currentThread().isInterrupted(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>);
   }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

  說明interrupted()方法檢查中斷狀態的同時，清除了中斷標誌位。 
  調用Thread.sleep()方法的時候，如果當前線程處於中斷狀態，那麼sleep()方法不會執行，同時會清除掉該狀態，並且拋出interruptedException異常。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">interruptMethod</span>() {

    Runnable runnable1 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Runnable() {
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; i++) {
                System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(i);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (Thread.currentThread().isInterrupted()) {
                    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread1中檢測到被中斷！"</span>);
                    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread1的中斷標誌："</span> + Thread.currentThread().isInterrupted());
                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 自己結束線程</span>
                }
                System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"thread1的中斷標誌："</span> + Thread.currentThread().isInterrupted());
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
                    Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>);
                } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
                    e.printStackTrace();
                    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">/*
                     *  sleep方法拋出這個異常之後會清除中斷狀態，所以需要重新設置中斷狀態
                     *  如果沒有重新設置線程爲中斷狀態，則sleep拋出異常後，會reset中斷狀態，
                     *  因此此案例還是會和main線程競爭
                     */</span>
                    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Thread.currentThread().interrupt();</span>
                    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"重新設置thread1的中斷標誌："</span> + Thread.currentThread().isInterrupted());
                }
            }
        }
    };

    final Thread thread1 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(runnable1);
    Runnable runnable2 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Runnable() {
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
                Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3000</span>);
                <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 設置thread1的中斷狀態</span>
                thread1.interrupt();
            } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };
       Thread thread2 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(runnable2);

       thread1.start();
       thread2.start();
       <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
        Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6000</span>);
    } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
        e.printStackTrace();
    }
    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"main線程檢測thread1的中斷標誌："</span> + thread1.isInterrupted());
    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"main線程檢測thread1是否存活："</span> + thread1.isAlive());
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li></ul>

  由於thread1中斷時，執行Thread.sleep()函數，會拋出InterruptedException，同時reset中斷標誌，所以thread1仍然處於Running/Runnable狀態，會和main線程競爭資源。運行結果如下： 
  這裏寫圖片描述
  在sleep的catch段中添加Thread.currentThread().interrupt();，重新設置中斷狀態，輸出結果： 
  這裏寫圖片描述

2.4 yield()

  yield有退讓的意思，暫停當前正在執行的線程對象，並執行其他線程。注意：這裏的其他也包含當前線程。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">yieldMethod</span>() {
    Thread thread1 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Runnable() {
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
                String threadName = Thread.currentThread().getName();
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">20</span>; i++) {
                    Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">500</span>);
                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (i == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>) {
                        System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(threadName + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" yield!"</span>);
                        Thread.currentThread().<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">yield</span>();
                    }
                    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(threadName + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"-->"</span> + i);
                }
            } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
                e.printStackTrace();
            }
        }
    });
    thread1.start();

    Thread thread2 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Runnable() {
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
                String threadName = Thread.currentThread().getName();
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">20</span>; i++) {
                    Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">500</span>);
                    System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(threadName + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"----->"</span> + i);
                }
            } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
                e.printStackTrace();
            }
        }
    });
    thread2.start();
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li></ul>

2.5 wait(), notify() and notifyAll()

  1. wait(): Causes the current thread to wait until another thread invokes thejava.lang.Object.notify() method or thejava.lang.Object.notifyAll()method for this object. The current thread must own this object’s monitor.
  2. notify(): Wakes up a single thread that is waiting on this object’s monitor.
  3. notifyAll(): Wakes up all threads that are waiting on this object’s monitor. 
      此處簡單給出Demo，後面會具體討論生產者-消費者這樣的線程通信問題。
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
 * 線程間傳遞的消息bean
 */</span>
class Message {
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String msg;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">Message</span>(String str){
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.msg=str;
    }
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">getMsg</span>() {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> msg;
    }
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setMsg</span>(String str) {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.msg=str;
    }
}

class Waiter implements Runnable{
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Message msg;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">Waiter</span>(Message m){
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.msg=m;
    }
    <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
        String name = Thread.currentThread().getName();
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">synchronized</span> (msg) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span>{
                System.out.println(name+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" waiting to get notified at time:"</span>+System.currentTimeMillis());
                <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">/*
                 *  The current thread must own this object's monitor.
                 *  意味着當前線程必須將msg作爲監視器
                 *  wait方法，暫時先把對象鎖給讓出來，給其它持有該鎖的對象用，
                 *  使當前線程處於阻塞狀態
                 */</span>
                <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//while(condition) { //注意在實際使用（如進程通信）時，要將wait放在循環當中，而不是if！</span>
                    msg.wait();
                <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//}</span>
            }<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span>(InterruptedException e){
                e.printStackTrace();
            }
            System.out.println(name+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" waiter thread got notified at time:"</span>+System.currentTimeMillis());
            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//process the message now</span>
            System.out.println(name+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" processed: "</span>+msg.getMsg());
        }
    }
}

class Notifier implements Runnable {

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Message msg;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">Notifier</span>(Message msg) {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.msg = msg;
    }
    <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">run</span>() {
        String name = Thread.currentThread().getName();
        System.out.println(name+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" started"</span>);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
            Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">synchronized</span> (msg) {
                msg.setMsg(name+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" Notifier work done"</span>);
                msg.notify();
                <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// msg.notifyAll();</span>
            }
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">waitNotifyNotifyAllMethod</span>() {
    Message msg = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Message(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"process it"</span>);
    Waiter waiter = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Waiter(msg);
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(waiter, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"waiter"</span>).start();

    Waiter waiter1 = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Waiter(msg);
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(waiter1, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"waiter1"</span>).start();

    Notifier notifier = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Notifier(msg);
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(notifier, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"notifier"</span>).start();
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li></ul>

  調用notify()時，只喚醒被msg.wait()阻塞的線程中的一個，而另一個線程仍讓處於阻塞狀態，所以程序進程未結束： 
  這裏寫圖片描述 
  調用notifyAll()時，喚醒被msg.wait()阻塞的所有線程，所以程序進程結束： 
  這裏寫圖片描述

站內首發文章
NicolasYan
發佈了39 篇原創文章 · 獲贊 3 · 訪問量 6萬+
私信 關注
發表評論
所有評論
還沒有人評論，想成為第一個評論的人麼? 請在上方評論欄輸入並且點擊發布.
相關文章

mybatis開啓MapperScannerConfigurer導致properties不生效

背景 spring和mybatis集成過程中，我們可以通過MapperFactoryBean的方式配置Mapper接口。但是這樣需要在配置文件中，爲每個mapper配置相同的代碼塊，浪費時間。關鍵對於代碼潔癖的人來說，一點不能忍。 <bea

原創 2024-02-07 13:55:41

Java字符串的一些理解

爲什麼要研究字符串？ 人機交互的過程中，文字、數字、字母、符號都是字符表現形式，這部分內容佔了人機信息交互的大部分內容，所以有必要明確一些基本問題。因此大部分數據類型都應該有字符串表達形式，我們在定義新類型的時候可以根據需要來定義新類型的

原創 2023-10-31 09:11:32

（二）java版spring boot 社交電子商務平臺-security簡單使用

security的簡單原理： 使用衆多的攔截器對url攔截，以此來管理權限。但是這麼多攔截器，不可能對其一一來講，主要講裏面核心流程的兩個。 首先，權限管理離不開登陸驗證的，所以登陸驗證攔截器AuthenticationProcessing

原創 2023-10-10 11:05:06

（三）java版spring cloud+spring boot+redis多租戶社交電子商務平臺-Spring Cloud實戰隨機端口

我們經常會需要啓動多個實例的情況來測試註冊中心、配置中心等基礎設施的高可用，也會用來測試客戶端負載均衡的調用等。但是，我們一個應用只能有一個端口號，這就使得在本機測試的時候，不得不爲同一個服務設置不同的端口來進行啓動。 在本地用不同端口啓動

原創 2023-10-10 11:05:04

如何使用 Java 反射？反射的用法及案例

簡介     Java Reflection，稱爲 Java 反射，是Java基礎部分的一個比較難的點。Reflection（反射）是被視爲動態語言的關鍵，通過反射機制，我們可以在運行時（runtime）獲取類的完整結構。例如，可以獲取到

原創 2023-10-10 02:23:57

最新美團面試集合（一面+二面+三面+重點技術面試題）附面試解析

一面 1. 簡短自我介紹 2. 事務的ACID，其中把事務的隔離性詳細解釋一遍 3. 髒讀、幻影讀、不可重複讀 4. 紅黑樹、二叉樹的算法 5. 平常用到哪些集合類？ArrayList和LinkedList區別？HashMap內部數據結構

原創 2023-10-10 01:43:49

Java程序員不想被裁員困擾，應該怎樣築基、發展才能越走越遠？

  當我們站在技術之路的原點，未來可能充滿了迷茫，也存在着很多不同的可能。在這個知識爆炸與終身學習/碎片化學習爲主的時代，我們面臨的問題之一就是如何進行有效學習，不僅能有效平衡廣度與深度，並且能真正的積澱下來，提升自己的研發效能。於筆者而

原創 2023-10-10 01:43:34

阿里巴巴Java開發手冊 梳理筆記 - finally 塊必須對資源對象、流對象進行關閉

阿里巴巴Java開發手冊 梳理筆記 - finally 塊必須對資源對象、流對象進行關閉 規約內容： 2.1 異常處理 6. 【強制】 finally 塊必須對資源對象、流對象進行關閉，有異常也要做 try - catch 。 說明：如果

原創 2023-08-02 10:29:06

java併發-CAS的理解

在Java方面，能夠實現多線程安全修改對象值得方法只有2個 1.原子操作 2.互斥方法 而在Java當中，或是其他語言中，基本上也都是使用CAS實現。CAS是比較並交換的意思，這個操作包含2個連續的操作，比較，還有賦值，因爲2個操作在cpu

原創 2023-05-29 01:40:21

java併發-Timer類的使用和原理

單線程輪詢並執行任務，有可能會導致飢餓。比較適合於一些具有一個任務的週期調度。 任務列表用數組存儲，元素最前面的元素是最先被執行的任務。 schedule方法是固定間隔執行，根據上一次執行的結束時間來定義間隔的開始時間 scheduleAt

原創 2023-03-28 01:52:22

java併發-ReadWriteLock代碼理解

創建的ReadWriteLock需要使用兩個方法來繼續創造2個對象，分別是ReadLock和WriteLock。 這兩個鎖對象的方法調用都會匯聚到ReadWriteLock的Sync類中。多個對象的方法調用匯聚到一個對象上面，這個設計模式是

原創 2023-03-28 01:52:20

java併發-synchronized關鍵字

synchronized關鍵字可以修飾普通方法，靜態方法，當修飾普通方法，鎖對象是當前對象，當修飾靜態方法，鎖對象是當前類的class synchroinzed關鍵字可以使用同步代碼塊實現同步，此時可以指定鎖對象。 同步方法的實現方式 同步

原創 2023-03-28 01:52:18

java併發-AQS總結-原理

AQS是Java多線程編程的重入鎖，管程，工具類的基礎類，是必須要掌握的。不掌握這個類，根本不能稱之爲合格的Java程序員。 即使是把這個類所有的代碼都背會，也是值得的。 如何標識已經有線程在執行呢？ 有兩個變量，一個state變量，一個e

原創 2023-03-28 01:52:16

java併發-緩存一致性協議和內存屏障的思考和理解

################這是之前的思考 內存屏障只是保證清空流水線，如何保證高速緩存的內容更新到最新或刷新到主存呢？這個問題突然想到了，不知道這個需要怎回答。 內存屏障保證的CPU執行執行序列能夠順序執行，而不是亂序執行。當然，前提

原創 2023-03-28 01:52:14

Java併發-volidate關鍵字

使用volidate關鍵字修飾的成員變量，保證可見性，也就是當一個線程修改這樣的成員變量後，其他的線程能夠立即看到這次的修改。有兩個方面的原因： 1.編譯器不優化對這樣的關鍵字修飾變量的一些訪問操作 2.對讀，寫這個關鍵字修飾的變量前後，會

原創 2023-03-28 01:52:13