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java 24种设计模式 含代码 java 24种设计模式 含代码

            </p>
            <p>&lt;cd&gt;<br>
              &lt;title&gt;Another Green World&lt;/title&gt;<br>
              &lt;year&gt;1978&lt;/year&gt;<br>
              &lt;artist&gt;Eno, Brian&lt;/artist&gt;<br>
              &lt;/cd&gt;<br>
            </p>
            <p>&lt;cd&gt;<br>
              &lt;title&gt;Greatest Hits&lt;/title&gt;<br>
              &lt;year&gt;1950&lt;/year&gt;<br>
              &lt;artist&gt;Holiday, Billie&lt;/artist&gt;<br>
              &lt;/cd&gt;<br>
            </p>
            <p>&lt;cd&gt;<br>
              &lt;title&gt;Taking Tiger Mountain (by strategy)&lt;/title&gt;<br>
              &lt;year&gt;1977&lt;/year&gt;<br>
              &lt;artist&gt;Eno, Brian&lt;/artist&gt;<br>
              &lt;/cd&gt;<br>
            </p>
            <p>....... </p>
            <p>&lt;/collection&gt;<br>
            </p>
          </td>
        </tr>
      </table>
      <p><br>
        虽然上面举例CD只有3张,CD可看成是大量重复的小类,因为其中成分只有三个字段,而且有重复的(歌唱者姓名).</p>
      <p>CD就是类似上面接口 Flyweight:</p>
      <table width="80%" border="0" cellspacing="3" cellpadding="3">
        <tr> 
          <td bgcolor="#CCCCCC"> 
            <p><br>
              public class CD {</p>
            <p>　　private String title;<br>
              　　private int year;<br>
              　　private Artist artist;<br>
              <br>
              　　public String getTitle() {　　return title;　}<br>
              　　public int getYear() {　　　　return year;　　}<br>
              　　public Artist getArtist() {　　　　return artist;　　}<br>
              <br>
              　　public void setTitle(String t){　　　　title = t;}<br>
              　　public void setYear(int y){year = y;}<br>
              　　public void setArtist(Artist a){artist = a;}<br>
              <br>
              }</p>
          </td>
        </tr>
      </table>
      <p>将&quot;歌唱者姓名&quot;作为可共享的ConcreteFlyweight:</p>
      <table width="80%" border="0" cellspacing="3" cellpadding="3">
        <tr> 
          <td bgcolor="#CCCCCC"> 
            <p>public class Artist {<br>
            </p>
            <p>　　//内部状态<br>
              　　private String name; </p>
            <p>　　// note that Artist is immutable.<br>
              　　String getName(){return name;}<br>
            </p>
            <p>　　Artist(String n){<br>
              　　　　name = n;<br>
              　　} <br>
              <br>
              }<br>
            </p>
          </td>
        </tr>
      </table>
      <p>再看看Flyweight factory,专门用来制造上面的可共享的ConcreteFlyweight:Artist</p>
      <table width="80%" border="0" cellspacing="3" cellpadding="3">
        <tr>
          <td bgcolor="#CCCCCC">
            <p>public class ArtistFactory {</p>
            <p>　　Hashtable pool = new Hashtable();<br>
              <br>
              　　Artist getArtist(String key){<br>
            </p>
            <p>　　　　Artist result;<br>
              　　　　result = (Artist)pool.get(key);<br>
              　　　　////产生新的Artist<br>
              　　　　if(result == null) {<br>
              　　　　　　result = new Artist(key);<br>
              　　　　　　pool.put(key,result);<br>
              　　　　　　<br>
              　　　　}<br>
              　　　 return result;<br>
              　 }<br>
              <br>
              }<br>
            </p>
            </td>
        </tr>
      </table>
      <p>当你有几千张甚至更多CD时,Flyweight模式将节省更多空间,共享的flyweight越多,空间节省也就越大.</p>
      <p>&nbsp;</p>
      <p>设计模式如何在具体项目中应用见<a href="../mybook/index.htm" target="_blank">《Java实用系统开发指南》</a><br>
        <br>
        <br>
      </p>
      <p>&nbsp;</p>
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