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<!doctype html>
<html class="no-js" lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>
Pumpkinor.io
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<li><label>Categories</label></li>
<li><a href="%E7%AC%94%E8%AE%B0-%E9%9D%9E%E5%8E%9F%E5%88%9B.html">笔记-非原创</a></li>
<li><a href="configuration.html">configuration</a></li>
<li><a href="after%20read.html">after read</a></li>
<li><a href="Memo.html">Memo</a></li>
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<div class="article">
<a class="clearlink" href="16349119429216.html">
<h1>数值计算-精度，舍入和溢出</h1>
<div class="a-content">
<div class="a-content-text">
<h4><a id="%E6%91%98%E5%BD%95" class="anchor" aria-hidden="true"><span class="octicon octicon-link"></span></a>摘录</h4>
<p>浮点数的表示、计算、舍入和格式化、溢出等涉及的一些坑：</p>
<ol>
<li>切记，要精确表示浮点数应该使用 BigDecimal。并且，使用 BigDecimal 的 Double 入参的构造方法同样存在精度丢失问题，应该使用 String 入参的构造方法或者 BigDecimal.valueOf 方法来初始化。</li>
<li>对浮点数做精确计算，参与计算的各种数值应该始终使用 BigDecimal，所有的计算都要通过 BigDecimal 的方法进行，切勿只是让 BigDecimal 来走过场。任何一个环节出现精度损失，最后的计算结果可能都会出现误差。</li>
<li>对于浮点数的格式化，如果使用 String.format 的话，需要认识到它使用的是四舍五入，可以考虑使用 DecimalFormat 来明确指定舍入方式。但考虑到精度问题，我更建议使用 BigDecimal 来表示浮点数，并使用其 setScale 方法指定舍入的位数和方式。</li>
<li>进行数值运算时要小心溢出问题，虽然溢出后不会出现异常，但得到的计算结果是完全错误的。我们考虑使用 Math.xxxExact 方法来进行运算，在溢出时能抛出异常，更建议对于可能会出现溢出的大数运算使用 BigInteger 类。</li>
</ol>
<p>总之，对于金融、科学计算等场景，请尽可能使用 BigDecimal 和 BigInteger，避免由精度和溢出问题引发难以发现，但影响重大的 Bug。</p>
</div>
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</a>
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<div class="more-left left">
<span class="date">2021/10/22</span>
<span>posted in </span>
<span class="posted-in"><a href='Java%20Mistake%20100.html'>Java Mistake 100</a></span>
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<a href="%E7%AC%94%E8%AE%B0-%E9%9D%9E%E5%8E%9F%E5%88%9B.html"><strong>笔记-非原创</strong></a>
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<a href="16512991592673.html">消息队列的技术选型</a>
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<a href="16381018403104.html">2021/11/28 算法学习开始</a>
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