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<td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>范圍示例</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>   第 3 頁（共11 頁）</nobr></font></td>
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<font size="2" face="Verdana, Arial, Helvetica">
<p>以下是檢索 <code>PersonImpl</code> 及其子類 <code>ManagerImpl</code> 的所有實例的部分程序。</p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
{
      System.out.println("Retrieving all people");
      // Retrieving all departments
      Extent ext = pm.getExtent(PersonImpl.class, true);
      Iterator i = ext.iterator();
      while (i.hasNext()) {
         PersonImpl person = (PersonImpl) i.next();
         System.out.println(
            "Person:  "
            + person.getLastName()
            + ", "
            + person.getFirstName());
      }
      ext.closeAll();
}
</code>
</pre>
<p>注：范圍是通過持久性管理器進行檢索的。其參數如下所示：</p>
<ol>


<li>實例類，范圍以它為基礎</li>


<li>是否應包含子類</li>


</ol>
<p>最后，請注意應關閉范圍。這就關閉了范圍上的所有迭代器。此后，所有迭代器都將從它們的 <code>hasNext</code> 方法返回 <code>false</code>。</p>
<p>完成范圍的檢索后，我們得到一個迭代器（就如同一個集合），然后對其內容進行遍歷。打印的集合內容是創建的所有雇員，包括所有經理，因為經理是雇員的子類。
</p>
<p>
<code>com.stereobeacon.jdo.tutorial.ExtentTest</code> 中有該類的代碼。您可以使用 extentTest.bat 文件運行它。在程序中還有一個顯示 <code>DepartmentImpl</code> 類檢索的示例。
</p>
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