⭐ 欢迎来到虫虫下载站！ | 📦 资源下载 📁 资源专辑 ℹ️ 关于我们
⭐ 虫虫下载站
📤 上传资源

📄 j-scjp-3-3.html

📁 sun公司认证课程scjp
💻 HTML
📖 第 1 页 / 共 2 页
字号:
🔍
12 
<td class="small" colspan="6"><a target="_blank" style="color: #ffffff;" href="http://202.95.2.149/help.htm">高级搜索</a><img alt="" height="1" width="1" border="0" src="../i/c.gif"></td>
</tr>
<tr>
<td colspan="6"><img alt="" height="4" width="390" border="0" src="../i/c.gif"></td>
</tr>
</form>
</table>
</td>
</tr>
<tr>
<td class="hbg" height="21" width="160"></td><td class="bbg" valign="top" height="21" colspan="2">　　<a href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/" class="mainlink">IBM 主页</a><span class="divider">　| </span><a href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/products/index.shtml" class="mainlink">产品与服务</a><span class="divider">　|　</span><a href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/support/index.shtml" class="mainlink">支持与下载</a><span class="divider">　|　</span><a href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/account/index.shtml" class="mainlink">个性化服务</a></td>
</tr>
</table>
<TABLE width="100%" cellspacing="0" cellpadding="0" border="0">
<TR>
<TD bgcolor="#ffffff" height="1" width="150"><IMG src="../i/c.gif" width="150" height="1"></TD>
</TR>
<TR>
<TD bgcolor="#cc6633" height="3" width="150"><IMG src="../i/c.gif" width="150" height="3"></TD>
</TR>
<TR>
<TD bgcolor="#333333" height="1" width="150"><IMG src="../i/c.gif" width="150" height="1"></TD>
</TR>
<TR>
<TD bgcolor="#000000" height="1" width="150"><IMG src="../i/c.gif" width="150" height="1"></TD>
</TR>
<TR>
<TD bgcolor="#ffffff" height="1" width="150"><IMG src="../i/c.gif" width="150" height="2"></TD>
</TR>
</TABLE>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td><font size="-1" face="Verdana, sans-serif"><a href="http://www.ibm.com/">IBM</a> : <a href="/developerWorks/cn/index.shtml">developerWorks 中国网站</a> : <a href="/developerWorks/cn/java/index.shtml">java</a> ： <a href="/developerWorks/cn/cnedu.nsf/java-onlinecourse-bytitle?OpenView&Count=500">教学 - 在线教程</a></font>
<br>
<img alt=" Java 认证成功之路，第 1 部分：SCJP " src="imagemaster/masthead.jpg"></td><td width="*" valign="bottom" align="right"><a border="0" href="j-scjp.zip"><img alt="下载 ZIP 文件" border="0" src="../i/icon-zip.gif"></a><a target="_blank" href="../tutorial_eng/index.html" border="0"><img alt="英文原文" border="0" src="../i/icon-source.gif"></a>
					
					
					
&nbsp;&nbsp;&nbsp;
				</td>
</tr>
<tr>
<td height="2" colspan="2"><img height="2" width="1" src="../i/c.gif"></td>
</tr>
</table>
<TABLE border="0" cellpadding="0" cellspacing="0" width="100%">
<TR>
<TD width="150" height="1" bgcolor="#000000" colspan="6"><IMG alt="" height="1" width="150" src="../i/c.gif"></TD>
</TR>
<TR>
<TD background="../i/sw-gold.gif"><a border="0" href="index.html" onMouseOver="iOver('topmain'); iOver('bottommain'); self.status=mainblurb; return true;" onMouseOut="iOut('topmain'); iOut('bottommain'); self.status=''; return true;"><img alt="主菜单" border="0" src="../i/main.gif" name="topmain"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topsection'); iOver('bottomsection'); self.status=sectionblurb; return true;" onMouseOut="iOut('topsection'); iOut('bottomsection'); self.status=''; return true;" href="index3.html"><img alt="章节菜单" border="0" src="../i/section.gif" name="topsection"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topfeedback'); iOver('bottomfeedback'); self.status=feedbackblurb; return true;" onMouseOut="iOut('topfeedback'); iOut('bottomfeedback'); self.status=''; return true;" href="j-scjp-11-3.html"><img alt="给出此教程的反馈意见" border="0" src="../i/feedback.gif" name="topfeedback"></a></TD><TD width="100%" background="../i/sw-gold.gif"><img src="../i/c.gif"></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topprevious'); iOver('bottomprevious'); self.status=previousblurb; return true;" onMouseOut="iOut('topprevious'); iOut('bottomprevious'); self.status=''; return true;" href="j-scjp-3-2.html"><img alt="上页" border="0" src="../i/previous.gif" name="topprevious"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topnext'); iOver('bottomnext'); self.status=nextblurb; return true;" onMouseOut="iOut('topnext'); iOut('bottomnext'); self.status=''; return true;" href="j-scjp-3-4.html"><img alt="下页" border="0" src="../i/next.gif" name="topnext"></a></TD>
</TR>
</TABLE>
<table bgcolor="ffffff" cellspacing="0" cellpadding="2" border="0" height="400" width="100%">
<tr valign="bottom">
<a name="navskip"></a><td height="25" colspan="4"><img alt="3.流程控制、断言和异常处理 " src="imagemaster/titlebar3.jpg" border="0" height="25" width="562"></td>
</tr>
<tr>
<td bgcolor="ffffff" width="15">&nbsp;</td><td bgcolor="ffffff" width="12">&nbsp;</td><td valign="top" align="left" bgcolor="ffffff" width="*">
<p>
<br>
<table cellspacing="0" cellpadding="0" border="0">
<tr>
<td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>异常处理 </b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>   第 3 页（共5 页）</nobr></font></td>
</tr>
</table>
<br>
<br>
</p>
<font size="2" face="Verdana, Arial, Helvetica">
<p>异常是 Java 对象，异常类是从 <code>java.lang.Throwable</code>派生出来的。 </p>
<p>抛出异常用于表示出现了异常情况，如访问超出数组大小的索引。异常可以是 checked 或者是 unchecked。 <code>RuntimeException</code> 和 <code>Error</code> 的子类称为 <i>unchecked 异常 </i>。所有从 <code>Exception</code> 继承的其他类都是 <i>checked 异常 </i>。所有可能抛出 checked 异常的方法都必须用 <code>throws</code> 关键词(有关关键词的更多内容请参阅 <a href="j-scjp-5-3.html">Java 关键词和标识符 </a>) 来声明异常，或者用 <code>try/catch</code> 块来处理异常。 </p>
<p>
						
<b>
							<code>try</code>/<code>catch</code> 块 </b>
						
<br>
可能抛出异常的代码被包围在 <code>try</code> 块中。可以提供一个或者多个 <code>catch</code> 子句来处理不同的异常类型： </p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
  try 
  {
    // code that might throw exceptions
  }
  catch(Exception e)
  { 
    //code to handle the exception 
  }
</code>
</pre>
<p>更特定的异常类型应该首先处理。例如，我们必须从特定到最一般的顺序排列 <code>catch</code> 块，否则就会出现编译时错误。 </p>
<p>例如，假设 <code>MyException</code> 继承自 <code>Exception</code>:</p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
  try 
  {
    throw new MyException();       
  }
  catch(Exception e) 
  {
    System.out.println("Exception");	
  }
  catch(MyException e) 
  {
    System.out.println("MyException");	
  }
</code>
</pre>
<p>这里编译器会报怨无法达到 <code>MyException</code> 的 <code>catch</code> 子句，因为所有抛出的异常都被第一个一般性的 <code>catch</code> 子句捕获了。 </p>
<p>
						
<b>
							<code>finally</code> 块 </b>
						
<br>
还可以提供 <code>finally</code> 块来执行任何清除操作。如果抛出一个异常，那么相匹配的 <code>catch</code> 子句就会执行，然后控制就会进入 <code>finally</code> 块（如果有的话）。 <code>finally</code> 块的语法如下： </p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
  try 
  {
    // code that throws exceptions
  }
  catch(Exception e)
  {
    // handle exception
  }
  finally
  {
    // cleanup code
  }
</code>
</pre>
<p>
						
<code>finally</code> 块即使在没有异常抛出的情况下也会执行。惟一的例外是当 <code>try</code> 或者 <code>catch</code> 块调用 <code>System.exit()</code> 时。一个 <code>try</code> 块应当有一个 <code>catch</code> 块或者有一个 <code>finally</code> 块，但是不一定要同时有这两者。 </p>
<p>
						
<b>声明和抛出异常 </b>
						
<br>
要在代码中显式地抛出异常，可使用 <code>throw</code> 关键词。 </p>
<p>方法可以抛出的 checked 异常必须用 <code>throws</code> 关键词(有关关键词的更多内容请参阅 <a href="j-scjp-5-3.html">Java 关键词和标识符 </a>)声明。例如： </p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
  void f() throws MyException
  {	
    if(x &gt; y) throw new MyException(); // MyException is a subclass of Exception
  }
</code>
</pre>
<br>
</font></td>
</tr>
</table>
<TABLE border="0" cellpadding="0" cellspacing="0" width="100%">
<TR>
<TD background="../i/sw-gold.gif"><a border="0" href="index.html" onMouseOver="iOver('topmain'); iOver('bottommain'); self.status=mainblurb; return true;" onMouseOut="iOut('topmain'); iOut('bottommain'); self.status=''; return true;"><img alt="主菜单" border="0" src="../i/main.gif" name="bottommain"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topsection'); iOver('bottomsection'); self.status=sectionblurb; return true;" onMouseOut="iOut('topsection'); iOut('bottomsection'); self.status=''; return true;" href="index3.html"><img alt="章节菜单" border="0" src="../i/section.gif" name="bottomsection"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topfeedback'); iOver('bottomfeedback'); self.status=feedbackblurb; return true;" onMouseOut="iOut('topfeedback'); iOut('bottomfeedback'); self.status=''; return true;" href="j-scjp-11-3.html"><img alt="给出此教程的反馈意见" border="0" src="../i/feedback.gif" name="bottomfeedback"></a></TD><TD width="100%" background="../i/sw-gold.gif"><img src="../i/c.gif"></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topprevious'); iOver('bottomprevious'); self.status=previousblurb; return true;" onMouseOut="iOut('topprevious'); iOut('bottomprevious'); self.status=''; return true;" href="j-scjp-3-2.html"><img alt="上页" border="0" src="../i/previous.gif" name="bottomprevious"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topnext'); iOver('bottomnext'); self.status=nextblurb; return true;" onMouseOut="iOut('topnext'); iOut('bottomnext'); self.status=''; return true;" href="j-scjp-3-4.html"><img alt="下页" border="0" src="../i/next.gif" name="bottomnext"></a></TD>
</TR>
<TR>
<TD width="150" height="1" bgcolor="#000000" colspan="6"><IMG alt="" height="1" width="150" src="../i/c.gif"></TD>
</TR>
</TABLE>
<TABLE width="100%" cellpadding="0" cellspacing="0" border="0">
<TR>
<TD width="100%">
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td><img alt="" height="1" width="1" src="../i/c.gif"></td>
</tr>
<tr valign="top">
<td class="bbg" height="21">　<a class="mainlink" href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/ibm/index.shtml">关于 IBM</a><span class="divider">　| </span><a class="mainlink" href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/ibm/privacy/index.shtml">隐私条约</a><span class="divider">　| </span><a class="mainlink" href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/ibm/legal/index.shtml">法律条款</a><span class="divider">　| </span><a class="mainlink" href="/developerWorks/cgi-bin/click.cgi?url=http://www-900.ibm.com/cn/ibm/contact/index.shtml">联系 IBM</a></td>
</tr>
</table>
</TD>
</TR>
</TABLE>
<script src="//www.ibm.com/common/stats/stats.js" language="JavaScript1.2" type="text/javascript"></script>
<noscript>
<img border="0" alt="" height="1" width="1" src="//stats.www.ibm.com/rc/images/uc.GIF?R=noscript"></noscript>
</body>
</html>
12

⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -