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<time class="level-item has-text-grey" datetime="2013-07-16T07:47:49.000Z">2013-07-16</time>
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5 分钟 读完 (大约 790 个字)
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<h1 class="title is-size-3 is-size-4-mobile has-text-weight-normal">
一起学java之异常简介
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<div class="content">
<h4 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h4><p>程序运行中不可能一帆风顺,就算代码没有问题,也不能保证用户总是按程序员的意思输入,不能保证操作系统永远正常运转,网络永远通畅,如果程序中出现问题,不及时处理,程序会挂起会自动退出,程序的健壮性会大大降低 </p>
<a id="more"></a>
<h4 id="try-catch-finally"><a href="#try-catch-finally" class="headerlink" title="try_catch_finally"></a>try_catch_finally</h4><p>1.我们已经见过的异常:两数相除,除数是0;数组越界;数字格式异常,空指针等等 </p>
<ul>
<li>举例: </li>
</ul>
<p><img src="/images/20191016155011.png" alt></p>
<ul>
<li>语法 </li>
</ul>
<figure class="highlight plain hljs"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">try{ </span><br><span class="line"></span><br><span class="line">//正常程序 </span><br><span class="line"></span><br><span class="line">}catch(异常类型 异常对象){ </span><br><span class="line"></span><br><span class="line">//异常处理 </span><br><span class="line"></span><br><span class="line">}finally{ </span><br><span class="line"></span><br><span class="line">//最后执行 </span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li><p>说明: </p>
<ul>
<li>java中把可能出现异常的地方用try监控起来,如果程序运行中,try块中出现异常,则终止try块中其他语句的执行,转到catch块中执行相应的异常处理,如果try块执行正常,则不执行catch块中的语句 </li>
<li>finally块中可以省略,如果有finally块中的语句,不管有没有异常,都会执行 </li>
<li>java中追求万物皆对象,当然我们抓到的异常其实是封装了具体异常信息的一个对象 </li>
</ul>
</li>
<li><p>举例: </p>
</li>
</ul>
<p><img src="/images/20191016155130.png" alt></p>
<ul>
<li>注意:<ul>
<li>多重catch,当一段代码中可能有多种异常时,可以在同一个try块后使用多重catch,需要注意的是,父类异常应该尽量放在后面,否则子类异常就捕获不到了 </li>
</ul>
</li>
</ul>
<h4 id="java中的异常"><a href="#java中的异常" class="headerlink" title="java中的异常"></a>java中的异常</h4><p>1.java中常见的异常可以在API文档中查到 </p>
<p>2.java中的异常 </p>
<p><img src="/images/20191016155344.png" alt></p>
<p>3.说明: </p>
<ul>
<li>Throwable继承自Object,Error和Exception类用于处理java中的异常,Throwable,Error,Exception类的实例和他们子类的实例都被JVM识别为异常对象 </li>
<li>Error和Error的子类被识别为致命的,程序无法修复的错误,很罕见,如VirtualMachineError,这类问题一般不希望用户的程序捕获他们,因此,一般不处理Error问题 </li>
<li>Exception类型的异常被认识为可控制的异常,可以在程序中捕获处理,其子类RuntimeException称为运行时异常,该类异常通过程序员的努力,基本上可以避免 </li>
<li>另外是非运行时异常,要求程序中必须用try_catch包围,程序在编译时就会检查是否对该类异常进行了处理,如果程序没有捕获非运行时异常,将无法通过编译 </li>
</ul>
<p>4.常见的异常 </p>
<p><img src="/images/20191016155448.png" alt></p>
<p>5.异常类的方法 </p>
<ul>
<li>java中的异常信息主要调用Throwable的几个方法进行处理,主要的方法有: <ul>
<li>printStackTrace():输出异常详细信息,包括异常原因,发生位置等 </li>
<li>getMessage():返回异常详细信息,但是无法跟踪到行 </li>
<li>说明:还有其他的一些方法,可以查阅API文档哦~~ </li>
</ul>
</li>
</ul>
<h4 id="自定义异常"><a href="#自定义异常" class="headerlink" title="自定义异常"></a>自定义异常</h4><p>1.系统定义的异常不能代表程序中所有的异常,有时需要自定义异常 </p>
<p>2.自定义异常通常是可控的,只要继承RuntimeException类就可以了 </p>
<h4 id="throw和throws"><a href="#throw和throws" class="headerlink" title="throw和throws"></a>throw和throws</h4><p>1.使用throw抛出异常 </p>
<p>2.异常捕获或者throws抛出异常给调用者 </p>
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<li><strong>本文标题：</strong><a href="https://blog.visutech.cn/1929845495.html">一起学java之异常简介</a></li>
<li><strong>本文作者：</strong><a href="https://blog.visutech.cn">程振奇 | smallodd</a></li>
<li><strong>本文链接：</strong><a href="https://blog.visutech.cn/1929845495.html">https://blog.visutech.cn/1929845495.html</a></li>
<li><strong>发布时间：</strong>2013-07-16</li>
<li><strong>版权声明：</strong>本博客所有文章除特别声明外，均采用 <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/deed.zh" rel="external nofollow" target="_blank">CC BY-NC-SA 4.0</a> 许可协议。转载请注明出处！
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