tij315.htm

这也是我们java老师给我们的thinking in java的一些资料

      sleep(duration);
    } <font color=#0000ff>catch</font> (InterruptedException e) {
      System.out.println(getName() + <font color=#004488>" was interrupted. "</font> +
        <font color=#004488>"isInterrupted(): "</font> + isInterrupted());
      <font color=#0000ff>return</font>;
    }
    System.out.println(getName() + <font color=#004488>" has awakened"</font>);
  }
}

<font color=#0000ff>class</font> Joiner <font color=#0000ff>extends</font> Thread {
  <font color=#0000ff>private</font> Sleeper sleeper;
  <font color=#0000ff>public</font> Joiner(String name, Sleeper sleeper) {
    <font color=#0000ff>super</font>(name);
    <font color=#0000ff>this</font>.sleeper = sleeper;
    start();
  }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> run() {
   <font color=#0000ff>try</font> {
      sleeper.join();
    } <font color=#0000ff>catch</font> (InterruptedException e) {
      <font color=#0000ff>throw</font> <font color=#0000ff>new</font> RuntimeException(e);
    }
    System.out.println(getName() + <font color=#004488>" join completed"</font>);
  }
}

<font color=#0000ff>public</font> <font color=#0000ff>class</font> Joining {
  <font color=#0000ff>private</font> <font color=#0000ff>static</font> Test monitor = <font color=#0000ff>new</font> Test();
  <font color=#0000ff>public</font> <font color=#0000ff>static</font> <font color=#0000ff>void</font> main(String[] args) {
    Sleeper
      sleepy = <font color=#0000ff>new</font> Sleeper(<font color=#004488>"Sleepy"</font>, 1500),
      grumpy = <font color=#0000ff>new</font> Sleeper(<font color=#004488>"Grumpy"</font>, 1500);
    Joiner
      dopey = <font color=#0000ff>new</font> Joiner(<font color=#004488>"Dopey"</font>, sleepy),
      doc = <font color=#0000ff>new</font> Joiner(<font color=#004488>"Doc"</font>, grumpy);
    grumpy.interrupt();
    monitor.expect(<font color=#0000ff>new</font> String[] {
      <font color=#004488>"Grumpy was interrupted. isInterrupted(): false"</font>,
      <font color=#004488>"Doc join completed"</font>,
      <font color=#004488>"Sleepy has awakened"</font>,
      <font color=#004488>"Dopey join completed"</font>
    }, Test.AT_LEAST + Test.WAIT);
  }
} <font color=#009900>///:~</font></PRE></FONT></BLOCKQUOTE><p><br></p>
<p>A <b>Sleeper</b> is a type of <b>Thread</b> that goes to sleep for a time specified in its constructor. In <b>run(&#160;)</b>, the call to <b>sleep(&#160;)</b> may terminate when the time expires, but it may also be interrupted. Inside the <b>catch</b> clause, the interruption is reported, along with the value of <b>isInterrupted(&#160;)</b>. When another thread calls <b>interrupt(&#160;)</b> on this thread, a flag is set to indicate that the thread has been interrupted. However, this flag is cleared when the exception is caught, so the result will always be false inside the <b>catch</b> clause. The flag is used for other situations where a thread may examine its interrupted state apart from the exception.<br></p>
<p>A <b>Joiner</b> is a thread that waits for a <b>Sleeper</b> to wake up by calling <b>join(&#160;)</b> on the <b>Sleeper</b> object. In <b>main(&#160;)</b>, each <b>Sleeper</b> has a <b>Joiner</b>, and you can see in the output that if the <b>Sleeper</b> is either interrupted or if it ends normally, the <b>Joiner</b> completes in conjunction with the <b>Sleeper</b>.<br></p>
<h3>
<a name="_Toc24775843"></a><a name="Heading17270"></a>Coding variations</h3>
<p>In the simple examples that you&#146;ve seen so far, the thread objects are all inherited from <b>Thread</b>. This makes sense because the objects are clearly only being created <i>as</i> threads and have no other behavior. However, your class may already be inheriting from another class, in which case you can&#146;t also inherit from <b>Thread</b> (Java doesn&#146;t support multiple inheritance). In this case, you can use the alternative approach of implementing the <b>Runnable</b> interface. <b>Runnable</b> specifies only that there be a <b>run(&#160;)</b> method implemented, and <b>Thread</b> also implements <b>Runnable</b>. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap14_2215" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p>This example demonstrates the basics:<br></p>

<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#009900>//: c13:RunnableThread.java</font>
<font color=#009900>// SimpleThread using the Runnable interface.</font>

<font color=#0000ff>public</font> <font color=#0000ff>class</font> RunnableThread <font color=#0000ff>implements</font> Runnable {
  <font color=#0000ff>private</font> <font color=#0000ff>int</font> countDown = 5;
  <font color=#0000ff>public</font> String toString() {
    <font color=#0000ff>return</font> <font color=#004488>"#"</font> + Thread.currentThread().getName() +
      <font color=#004488>": "</font> + countDown;
  }
  <font color=#0000ff>public</font> <font color=#0000ff>void</font> run() {
    <font color=#0000ff>while</font>(<font color=#0000ff>true</font>) {
      System.out.println(<font color=#0000ff>this</font>);
      <font color=#0000ff>if</font>(--countDown == 0) <font color=#0000ff>return</font>;
    }
  }
  <font color=#0000ff>public</font> <font color=#0000ff>static</font> <font color=#0000ff>void</font> main(String[] args) {
    <font color=#0000ff>for</font>(<font color=#0000ff>int</font> i = 1; i &lt;= 5; i++)
      <font color=#0000ff>new</font> Thread(<font color=#0000ff>new</font> RunnableThread(), <font color=#004488>""</font> + i).start();
    <font color=#009900>// Output is like SimpleThread.java</font>
  }
} <font color=#009900>///:~</font></PRE></FONT></BLOCKQUOTE><p><br></p>
<p>The only thing required by a <b>Runnable</b> class is a <b>run(&#160;)</b> method, but if you want to do anything else to the <b>Thread</b> object (such as <b>getName(&#160;) </b>in <b>toString(&#160;)</b>) you must explicitly get a reference to it by calling <b>Thread.currentThread(&#160;)</b>. This particular <b>Thread</b> constructor takes a <b>Runnable</b> and a name for the thread.<br></p>
<p>When something has a <a name="Index1551"></a><a name="Index1552"></a><a name="Index1553"></a><b>Runnable</b> interface, it simply means that it has a <b>run(&#160;)</b> method, but there&#146;s nothing special about that&#151;it doesn&#146;t produce any innate threading abilities, like those of a class inherited from <b>Thread</b>. So to produce a thread from a <b>Runnable</b> object, you must create a separate <b>Thread</b> object as shown in this example, handing the <b>Runnable</b> object to the special <b>Thread </b>constructor. You can then call <b>start(&#160;)</b> for that thread, which performs the usual initialization and then calls <b>run(&#160;)</b>. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap14_2217" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p>The convenient aspect about the <b>Runnable interface</b> is that everything belongs to the same class; that is, <b>Runnable</b> allows a mixin in combination with a base class and other interfaces. If you need to access something, you simply do it without going through a separate object. However, inner classes have this same easy access to all the parts of an outer class, so member access is not a compelling reason to use <b>Runnable</b> as a mixin rather than an inner subclass of <b>Thread</b>. <font size="-2"><a href="mailto:[e-mail]?Subject=[TIJ3]Chap14_2219" title="Send BackTalk Comment">Feedback</a></font><br></p>
<p>When you use <b>Runnable</b>, you&#146;re generally saying that you want to create a <i>process</i> in a piece of code&#151;implemented in the <b>run(&#160;)</b> method&#151;rather than an object representing that process. This is a matter of some debate, depending on whether you feel that it makes more sense to represent a thread as an object or as a completely different entity, a process.<sup><a name="fnB68" href="#fn68">[68]</a></sup> If you choose to think of it as a process, then you are freed from the object-oriented imperative that &#147;everything is an object.&#148; This also means that there&#146;s no reason to make your whole class <b>Runnable</b> if you only want to start a process to drive some part of your program. Because of this, it often makes more sense to hide your threading code inside your class by using an inner class, as shown here:<br></p>

<BLOCKQUOTE><FONT SIZE = "+1"><PRE><font color=#009900>//: c13:ThreadVariations.java</font>
<font color=#009900>// Creating threads with inner classes.</font>
<font color=#0000ff>import</font> com.bruceeckel.simpletest.*;

<font color=#009900>// Using a named inner class:</font>
<font color=#0000ff>class</font> InnerThread1 {
  <font color=#0000ff>private</font> <font color=#0000ff>int</font> countDown = 5;
  <font color=#0000ff>private</font> Inner inner;
  <font color=#0000ff>private</font> <font color=#0000ff>class</font> Inner <font color=#0000ff>extends</font> Thread {
    Inner(String name) {
      <font color=#0000ff>super</font>(name);
      start();
    }
    <font color=#0000ff>public</font> <font color=#0000ff>void</font> run() {
      <font color=#0000ff>while</font>(<font color=#0000ff>true</font>) {
        System.out.println(<font color=#0000ff>this</font>);
        <font color=#0000ff>if</font>(--countDown == 0) <font color=#0000ff>return</font>;
        <font color=#0000ff>try</font> {
          sleep(10);
        } <font color=#0000ff>catch</font> (InterruptedException e) {
          <font color=#0000ff>throw</font> <font color=#0000ff>new</font> RuntimeException(e);
        }
      }
    }
    <font color=#0000ff>public</font> String toString() {
      <font color=#0000ff>return</font> getName() + <font color=#004488>": "</font> + countDown;
    }
  }
  <font color=#0000ff>public</font> InnerThread1(String name) {
    inner = <font color=#0000ff>new</font> Inner(name);
  }
}

<font color=#009900>// Using an anonymous inner class:</font>
<font color=#0000ff>class</font> InnerThread2 {
  <font color=#0000ff>private</font> <font color=#0000ff>int</font> countDown = 5;
  <font color=#0000ff>private</font> Thread t;
  <font color=#0000ff>public</font> InnerThread2(String name) {
    t = <font color=#0000ff>new</font> Thread(name) {
      <font color=#0000ff>public</font> <font color=#0000ff>void</font> run() {
        <font color=#0000ff>while</font>(<font color=#0000ff>true</font>) {
          System.out.println(<font color=#0000ff>this</font>);
          <font color=#0000ff>if</font>(--countDown == 0) <font color=#0000ff>return</font>;
          <font color=#0000ff>try</font> {
            sleep(10);
          } <font color=#0000ff>catch</font> (InterruptedException e) {
            <font color=#0000ff>throw</font> <font color=#0000ff>new</font> RuntimeException(e);
          }
        }
      }
      <font color=#0000ff>public</font> String toString() {
        <font color=#0000ff>return</font> getName() + <font color=#004488>": "</font> + countDown;
      }
    };
    t.start();
  }
}

<font color=#009900>// Using a named Runnable implementation:</font>
<font color=#0000ff>class</font> InnerRunnable1 {
  <font color=#0000ff>private</font> <font color=#0000ff>int</font> countDown = 5;
  <font color=#0000ff>private</font> Inner inner;
  <font color=#0000ff>private</font> <font color=#0000ff>class</font> Inner <font color=#0000ff>implements</font> Runnable {
    Thread t;