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Java中字符串及正则表达式简介.html
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Java中字符串及正则表达式简介.html
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<!doctype html>
<html>
<head>
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<div id='write' class = 'is-node'><p></p><h1><a name='header-c362' class='md-header-anchor '></a>Java中字符串及正则表达式简介</h1><p>教师：<a href='http://nlp.fudan.edu.cn/xpqiu'>邱锡鹏</a> 微博：<a href='http://weibo.com/xpqiu'>@邱锡鹏</a></p><p>助教：施展、龚经经</p><p>复旦大学 计算机学院 大数据学院</p><div class='md-toc' mdtype='toc'><p class="md-toc-content"><span class="md-toc-item md-toc-h1" data-ref="c362"><a class="md-toc-inner" href="#header-c362">Java中字符串及正则表达式简介</a></span><span class="md-toc-item md-toc-h3" data-ref="c364"><a class="md-toc-inner" href="#header-c364">1. 字符串（String）简介</a></span><span class="md-toc-item md-toc-h4" data-ref="c365"><a class="md-toc-inner" href="#header-c365">1.1 创建字符串</a></span><span class="md-toc-item md-toc-h4" data-ref="c378"><a class="md-toc-inner" href="#header-c378">1.2 基本操作</a></span><span class="md-toc-item md-toc-h5" data-ref="c379"><a class="md-toc-inner" href="#header-c379">1.2.1 判断两个字符串内容是否一致</a></span><span class="md-toc-item md-toc-h5" data-ref="c393"><a class="md-toc-inner" href="#header-c393">1.2.2 获取方法</a></span><span class="md-toc-item md-toc-h5" data-ref="c415"><a class="md-toc-inner" href="#header-c415">1.2.3判断方法</a></span><span class="md-toc-item md-toc-h5" data-ref="c440"><a class="md-toc-inner" href="#header-c440">1.2.4 转换方法</a></span><span class="md-toc-item md-toc-h5" data-ref="c455"><a class="md-toc-inner" href="#header-c455">1.2.5 其它方法</a></span><span class="md-toc-item md-toc-h4" data-ref="c483"><a class="md-toc-inner" href="#header-c483">1.3 重要特性</a></span><span class="md-toc-item md-toc-h4" data-ref="c495"><a class="md-toc-inner" href="#header-c495">1.4 StringBuffer类</a></span><span class="md-toc-item md-toc-h5" data-ref="c496"><a class="md-toc-inner" href="#header-c496">1.4.1 构造对象:</a></span><span class="md-toc-item md-toc-h5" data-ref="c501"><a class="md-toc-inner" href="#header-c501">1.4.2 基本操作:</a></span><span class="md-toc-item md-toc-h4" data-ref="c551"><a class="md-toc-inner" href="#header-c551">1.5 其它字符串缓冲类</a></span><span class="md-toc-item md-toc-h3" data-ref="c558"><a class="md-toc-inner" href="#header-c558">2 正则表达式</a></span><span class="md-toc-item md-toc-h4" data-ref="c561"><a class="md-toc-inner" href="#header-c561">2.1 表示法则</a></span><span class="md-toc-item md-toc-h5" data-ref="c562"><a class="md-toc-inner" href="#header-c562">2.1.1 预定义字符类</a></span><span class="md-toc-item md-toc-h5" data-ref="c588"><a class="md-toc-inner" href="#header-c588">2.1.2 数量词</a></span><span class="md-toc-item md-toc-h5" data-ref="c616"><a class="md-toc-inner" href="#header-c616">2.1.3 范围词</a></span><span class="md-toc-item md-toc-h4" data-ref="c636"><a class="md-toc-inner" href="#header-c636">2.2 主要应用</a></span><span class="md-toc-item md-toc-h5" data-ref="c647"><a class="md-toc-inner" href="#header-c647">2.2.1 匹配</a></span><span class="md-toc-item md-toc-h5" data-ref="c654"><a class="md-toc-inner" href="#header-c654">2.2.2 切割</a></span><span class="md-toc-item md-toc-h5" data-ref="c667"><a class="md-toc-inner" href="#header-c667">2.2.3 替换</a></span><span class="md-toc-item md-toc-h5" data-ref="c673"><a class="md-toc-inner" href="#header-c673">2.2.4 查找</a></span></p></div><h3><a name='header-c364' class='md-header-anchor '></a>1. 字符串（String）简介</h3><h4><a name='header-c365' class='md-header-anchor '></a>1.1 创建字符串</h4><p>方式1: String str1 = “abc”</p><p>方式2: String str2 = new String(“abc”)</p><p>其中new String()中的参数形式可以有多种 如:String(bytes[] byte) 接受一个字节数组 String(char[] value) 接受一个字符数组 String(String str) 接受一个字符串对象 使用字节数组或者字符数组都可以构建字符串对象</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str1</span> <span class="cm-operator">=</span> <span class="cm-string">"abc"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str2</span> <span class="cm-operator">=</span> <span class="cm-keyword">new</span> <span class="cm-variable-3">String</span>(<span class="cm-string">"abc"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">byte</span>[] <span class="cm-variable">bt</span> <span class="cm-operator">=</span> {<span class="cm-number">97</span>,<span class="cm-number">98</span>,<span class="cm-number">99</span>};</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str3</span> <span class="cm-operator">=</span> <span class="cm-keyword">new</span> <span class="cm-variable-3">String</span>(<span class="cm-variable">bt</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">char</span>[] <span class="cm-variable">ch</span> <span class="cm-operator">=</span> {<span class="cm-string">'a'</span>,<span class="cm-string">'b'</span>,<span class="cm-string">'c'</span>};</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str4</span> <span class="cm-operator">=</span> <span class="cm-keyword">new</span> <span class="cm-variable-3">String</span>(<span class="cm-variable">ch</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"str1 = "</span><span class="cm-operator">+</span> <span class="cm-variable">str1</span> <span class="cm-operator">+</span><span class="cm-string">" str2 = "</span> <span class="cm-operator">+</span><span class="cm-variable">str2</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"str3 = "</span><span class="cm-operator">+</span> <span class="cm-variable">str3</span> <span class="cm-operator">+</span><span class="cm-string">" str4 = "</span> <span class="cm-operator">+</span><span class="cm-variable">str4</span>);</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 179px;"></div></div></div></pre><p>结果：</p><p>str1 = abc str2 = abc
str3 = abc str4 = abc</p><h4><a name='header-c378' class='md-header-anchor '></a>1.2 基本操作</h4><h5><a name='header-c379' class='md-header-anchor '></a>1.2.1 判断两个字符串内容是否一致</h5><ol><li>str1 == str2 判别的是两个字符串的内存地址 </li><li>str1.equals(str2) 判别的是两个字符串的内容</li></ol><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str1</span> <span class="cm-operator">=</span> <span class="cm-string">"hello"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str2</span> <span class="cm-operator">=</span> <span class="cm-keyword">new</span> <span class="cm-variable-3">String</span>(<span class="cm-string">"hello"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"str1 == str2?"</span> <span class="cm-operator">+</span>(<span class="cm-variable">str1</span> <span class="cm-operator">==</span><span class="cm-variable">str2</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"str1，str2内容是否相同？"</span><span class="cm-operator">+</span>(<span class="cm-variable">str1</span>.<span class="cm-variable">equals</span>(<span class="cm-variable">str2</span>)));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 90px;"></div></div></div></pre><p>结果：</p><p>str1 == str2?false
str1，str2内容是否相同？true</p><h5><a name='header-c393' class='md-header-anchor '></a>1.2.2 获取方法</h5><ol><li>获取字符串长度:int length() 长度即字符个数 </li><li>获取特定位置的字符 char charAt(int index)</li><li>获取特定字符的位置 int indexOf(String str) 返回子串第一次出现 的索引值,如果子串没出现在字符串中,则返回-1</li><li>获取最后一个字符位置 int lastIndexOf(String str) 返回子串最后 一次出现的索引值,如果子串没出现在字符串中,则返回-1</li></ol><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str</span> <span class="cm-operator">=</span> <span class="cm-string">"abc中国ab中国"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串的长度： "</span> <span class="cm-operator">+</span> <span class="cm-variable">str</span>.<span class="cm-variable">length</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"索引值3对应的字符： "</span> <span class="cm-operator">+</span> <span class="cm-variable">str</span>.<span class="cm-variable">charAt</span>(<span class="cm-number">3</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"子字符串第一次出现的位置： "</span> <span class="cm-operator">+</span> <span class="cm-variable">str</span>.<span class="cm-variable">indexOf</span>(<span class="cm-string">"中国"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"子字符串最后一次出现的位置： "</span> <span class="cm-operator">+</span> <span class="cm-variable">str</span>.<span class="cm-variable">lastIndexOf</span>(<span class="cm-string">"中国"</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 112px;"></div></div></div></pre><p>结果：</p><p>字符串的长度： 9
索引值3对应的字符： 中
子字符串第一次出现的位置： 3
子字符串最后一次出现的位置： 7</p><h5><a name='header-c415' class='md-header-anchor '></a>1.2.3判断方法</h5><ol><li>是否以指定字符结束 boolean endsWith(String str) </li><li>是否长度为0 booleanisEmpty()</li><li>是否包含指定序列 boolean contains(String str)</li><li>是否内容一致 boolean equals(Object obj)</li><li>忽略大小写是否内容一致booleanequalsIngoreCase(String str)</li></ol><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str</span> <span class="cm-operator">=</span> <span class="cm-string">"Demo.java"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"是否以指定字符串结束? "</span> <span class="cm-operator">+</span><span class="cm-variable">str</span>.<span class="cm-variable">endsWith</span>(<span class="cm-string">"va"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str3</span> <span class="cm-operator">=</span> <span class="cm-string">""</span>;</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串是否为空？ "</span> <span class="cm-operator">+</span><span class="cm-variable">str3</span>.<span class="cm-variable">isEmpty</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串是否包含指定内容？ "</span> <span class="cm-operator">+</span><span class="cm-variable">str</span>.<span class="cm-variable">contains</span>(<span class="cm-string">"java"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串内容是否一致（忽略大小写）?"</span> <span class="cm-operator">+</span><span class="cm-variable">str</span>.<span class="cm-variable">equalsIgnoreCase</span>(<span class="cm-string">"DEMO.JAVA"</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 134px;"></div></div></div></pre><p>结果：</p><p>是否以指定字符串结束? true
字符串是否为空？ true
字符串是否包含指定内容？ true
字符串内容是否一致（忽略大小写）? true</p><h5><a name='header-c440' class='md-header-anchor '></a>1.2.4 转换方法</h5><ol><li>将字符串转换为字符数组 char[] toCharArray()</li></ol><ol><li>将字符串转换为字节数组 byte[] getBytes()</li></ol><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str</span> <span class="cm-operator">=</span> <span class="cm-string">"Demo.java"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">char</span>[] <span class="cm-variable">ch</span> <span class="cm-operator">=</span> <span class="cm-variable">str</span>.<span class="cm-variable">toCharArray</span>();</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">byte</span>[] <span class="cm-variable">bt</span> <span class="cm-operator">=</span> <span class="cm-variable">str</span>.<span class="cm-variable">getBytes</span>();</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符数组内容： "</span> <span class="cm-operator">+</span><span class="cm-variable">Arrays</span>.<span class="cm-variable">toString</span>(<span class="cm-variable">ch</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字节数组内容： "</span> <span class="cm-operator">+</span><span class="cm-variable">Arrays</span>.<span class="cm-variable">toString</span>(<span class="cm-variable">bt</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 112px;"></div></div></div></pre><p>结果：</p><p>字符数组内容： [D, e, m, o, ., j, a, v, a]
字节数组内容： [68, 101, 109, 111, 46, 106, 97, 118, 97]</p><h5><a name='header-c455' class='md-header-anchor '></a>1.2.5 其它方法</h5><ol><li>替换 String replace(String target, String replacement) 顺序替换</li><li>切割 String[] split(String str)</li><li>截取子串 String substring(int begin, int end) 取头舍尾</li><li>转大写 String toUpperCase()</li><li>转小写 String toLowerCase()</li><li>去除空格 String trim() 去除字符串首尾的空格 (包括\t之类字符,但全角空格去不掉)</li></ol><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str</span> <span class="cm-operator">=</span> <span class="cm-string">"abbbaabbaaa"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"指定新内容替换旧内容： "</span> <span class="cm-operator">+</span><span class="cm-variable">str</span>.<span class="cm-variable">replace</span>(<span class="cm-string">"aa"</span>, <span class="cm-string">"cc"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str1</span> <span class="cm-operator">=</span> <span class="cm-string">"aa-cc-Ee-dd"</span>;</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str2</span> <span class="cm-operator">=</span> <span class="cm-string">" sdasd\t"</span>;</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span>[] <span class="cm-variable">arr</span> <span class="cm-operator">=</span> <span class="cm-variable">str1</span>.<span class="cm-variable">split</span>(<span class="cm-string">"-"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串数组内容： "</span> <span class="cm-operator">+</span><span class="cm-variable">Arrays</span>.<span class="cm-variable">toString</span>(<span class="cm-variable">arr</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"从索引值处截取子串： "</span> <span class="cm-operator">+</span><span class="cm-variable">str1</span>.<span class="cm-variable">substring</span>(<span class="cm-number">3</span>,<span class="cm-number">5</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"转大写： "</span> <span class="cm-operator">+</span><span class="cm-variable">str1</span>.<span class="cm-variable">toUpperCase</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"转小写： "</span> <span class="cm-operator">+</span><span class="cm-variable">str1</span>.<span class="cm-variable">toLowerCase</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"去除头尾空格： "</span> <span class="cm-operator">+</span><span class="cm-variable">str2</span>.<span class="cm-variable">trim</span>());</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 224px;"></div></div></div></pre><p>结果：</p><p>从索引值处截取子串： cc
转大写： AA-CC-EE-DD
转小写： aa-cc-ee-dd
去除头尾空格： sdasd</p><h4><a name='header-c483' class='md-header-anchor '></a>1.3 重要特性</h4><p>字符串是常量,它们的值在创建后不能修改,字符串的内容一旦发生变化,那么马上会创建一个新的对象。</p><p>字符串的内容不适宜频繁修改,因为一旦修改马上就会创建一个新的对象。</p><p>如果需要频繁修改字符串的内容,建议使用字符串缓冲类(StringBuffer)。StringBuffer 其实就是一个存储字符的容器</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str3</span> <span class="cm-operator">=</span> <span class="cm-string">"Hello"</span>;</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">String</span> <span class="cm-variable">str4</span> <span class="cm-operator">=</span> <span class="cm-variable">str3</span> <span class="cm-operator">+</span> <span class="cm-string">"World"</span>;</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Str3和Str4在相同的存储位置吗？ "</span> <span class="cm-operator">+</span> (<span class="cm-variable">str3</span> <span class="cm-operator">==</span> <span class="cm-variable">str4</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 67px;"></div></div></div></pre><p>结果：</p><p>Str3和Str4在相同的存储位置吗？ false</p><h4><a name='header-c495' class='md-header-anchor '></a>1.4 StringBuffer类</h4><h5><a name='header-c496' class='md-header-anchor '></a>1.4.1 构造对象:</h5><p>StringBuffer sb = new StringBuffer() </p><p>StringBuffer 底层是依赖了一个字符数组才能存储字符数据的,该字符数组默认的初始容量是16,如果字符数组的长度不够使用时,自动增长一倍。 </p><h5><a name='header-c501' class='md-header-anchor '></a>1.4.2 基本操作:</h5><p>增加 </p><p>append(xxx) 可添加任意类型的数据</p><p>Insert(int offset, xxx) 可插入任意类型的数据-String类没有该方法 </p><p>删除</p><p>delete(int start, int end) 根据指定的头尾索引值删除对应内容 - String类没有该方法</p><p>deleteCharAt(int index) 根据指定索引值删除一个字符</p><p>修改</p><p>replace(int start, int end, String str) 根据指定头尾索引值替换成指定内容</p><p>reverse() 翻转字符串缓冲类的内容</p><p>setCharAt(int index) 把指定索引值的字符替换指定字符 </p><p>substring(int start, int end) 根据指定索引值截取子串</p><p>查找 </p><p>indexOf(String str, int index)</p><p>capacity() 查看字符数组的长度(非已存储的字符 串长度)</p><p>length() 查看存储字符的个数lcharAt() 查看字符串指定位置的字符</p><p>toString() 把字符串缓冲类的内容转换成字符串返回 </p><p>总结：若对字符串有较多增删操作,使stringbuffer类更好</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">StringBuffer</span> <span class="cm-variable">sb</span> <span class="cm-operator">=</span> <span class="cm-keyword">new</span> <span class="cm-variable-3">StringBuffer</span>();</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">append</span>(<span class="cm-string">"abc"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">append</span>(<span class="cm-atom">true</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">append</span>(<span class="cm-number">3.14</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">insert</span>(<span class="cm-number">5</span>, <span class="cm-string">"INS"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">delete</span>(<span class="cm-number">2</span>, <span class="cm-number">4</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">deleteCharAt</span>(<span class="cm-number">3</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">replace</span>(<span class="cm-number">3</span>,<span class="cm-number">5</span>, <span class="cm-string">"Nature"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">sb</span>.<span class="cm-variable">reverse</span>();</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符串缓冲类里的内容： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>.<span class="cm-variable">substring</span>(<span class="cm-number">3</span>,<span class="cm-number">7</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable-3">int</span> <span class="cm-variable">index</span> <span class="cm-operator">=</span> <span class="cm-variable">sb</span>.<span class="cm-variable">indexOf</span>(<span class="cm-string">"rba"</span>,<span class="cm-number">2</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"索引值为： "</span> <span class="cm-operator">+</span> <span class="cm-variable">index</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"字符数组的长度： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>.<span class="cm-variable">capacity</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"存储字符的长度： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>.<span class="cm-variable">length</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"索引值指定的字符： "</span> <span class="cm-operator">+</span> <span class="cm-variable">sb</span>.<span class="cm-variable">charAt</span>(<span class="cm-number">3</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 470px;"></div></div></div></pre><p>结果：</p><p>字符串缓冲类里的内容： abctrue3.14
字符串缓冲类里的内容： abctrINSue3.14
字符串缓冲类里的内容： abrINSue3.14
字符串缓冲类里的内容： abrNSue3.14
字符串缓冲类里的内容： abrNatureue3.14
字符串缓冲类里的内容： 41.3euerutaNrba
字符串缓冲类里的内容： 3eue
索引值为： 12
字符数组的长度： 16
存储字符的长度： 15
索引值指定的字符： 3</p><h4><a name='header-c551' class='md-header-anchor '></a>1.5 其它字符串缓冲类</h4><p>StringBuilder类 与 StringBuffer类</p><p>相同点: 两个类都是字符串缓冲类,两个类方法都是一致的</p><p>不同点: StringBuffer是线程安全的,操作效率低 StringBuilder 是线程非安全的,操作效率高</p><h3><a name='header-c558' class='md-header-anchor '></a>2 正则表达式</h3><p>正则表达式是用于操作字符串的一个规则,正则 表达式的规则使用了特殊的符号表示</p><h4><a name='header-c561' class='md-header-anchor '></a>2.1 表示法则</h4><h5><a name='header-c562' class='md-header-anchor '></a>2.1.1 预定义字符类</h5><p>. 任意字符</p><p>\D 非数字:［^0-9］</p><p>\d 数字: [0-9]</p><p>\s 空白字符:[\t\n\x0B\f\r] </p><p>\S 非空白字符: ［^\s］</p><p>\w 单词字符: [a-zA-Z_0-9] </p><p>\W 非单词字符: ［^\w］</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Any:"</span><span class="cm-operator">+</span><span class="cm-string">"a"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"."</span>));</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Digit:"</span><span class="cm-operator">+</span><span class="cm-string">"1"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\d"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Nondigit:"</span><span class="cm-operator">+</span><span class="cm-string">"a"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\D"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Blank:"</span><span class="cm-operator">+</span><span class="cm-string">"\n"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\s"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"NonBlank:"</span><span class="cm-operator">+</span><span class="cm-string">"\n"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\s"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Word:"</span><span class="cm-operator">+</span><span class="cm-string">"w"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\w"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"Nonword:"</span><span class="cm-operator">+</span><span class="cm-string">"#"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\W"</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 157px;"></div></div></div></pre><p>结果：</p><p>Any:true
Digit:true
Nondigit:true
Blank:true
NonBlank:true
Word:true
Nonword:true</p><h5><a name='header-c588' class='md-header-anchor '></a>2.1.2 数量词</h5><p>X?0 次或一次 </p><p>X+至少出现一次</p><p>X* 0次或者多次 </p><p>X{n} n 次</p><p>X{n,} n 次及以上</p><p>X{n,m} n~m 次</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"<=1, ?:"</span><span class="cm-operator">+</span><span class="cm-string">"a"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\w?"</span>));</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"0or>1, *:"</span><span class="cm-operator">+</span><span class="cm-string">""</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\d*"</span>)<span class="cm-operator">+</span><span class="cm-string">"22"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\d*"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">">=1, +:"</span><span class="cm-operator">+</span><span class="cm-string">"a"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\D+"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"n, {n}"</span><span class="cm-operator">+</span><span class="cm-string">"\n\r\n"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\s{3}"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"n~m, {n,m}:"</span><span class="cm-operator">+</span><span class="cm-string">"1232132"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\d{1,9}"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">">=n, {n,}:"</span><span class="cm-operator">+</span><span class="cm-string">"www"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"\\w{2,}"</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 134px;"></div></div></div></pre><p>结果：</p><p><=1, ?:true</p><p>0or>1, *: true true</p><p>=1, +:true</p><p>n, {n}true</p><p>n~m, {n,m}:true</p><p>=n, {n,}:true</p><h5><a name='header-c616' class='md-header-anchor '></a>2.1.3 范围词</h5><p>[abc] a,b或者c</p><p>[^abc] 除a,b,c任意字符 </p><p>[a-zA-Z] a-z或A-Z的任字符 </p><p>[a-d[m-p]] a到d或m到p </p><p>[a-z&&[def]] d,e或f(交集) </p><p>范围词内无论多长, 都只匹配一个字符而已</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"[xxx]"</span><span class="cm-operator">+</span><span class="cm-string">"a"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"[abv]"</span>));</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"[x-x]"</span><span class="cm-operator">+</span><span class="cm-string">"3"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"[1-9]"</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-string">"[^xx]"</span><span class="cm-operator">+</span><span class="cm-string">"a"</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"[^bc]"</span>));</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 67px;"></div></div></div></pre><p>结果：</p><p>[xxx]true
[x-x]true
[^xx]true</p><h4><a name='header-c636' class='md-header-anchor '></a>2.2 主要应用</h4><p>正则表达式对字符串操作的主要应用 </p><p>匹配 matches()</p><p>切割 split()</p><p>替换 replaceAll(String regex, String replacement)</p><p>查找 查找需要使用的对象:Pattern(正则对象) Matcher(匹配器对象)</p><h5><a name='header-c647' class='md-header-anchor '></a>2.2.1 匹配</h5><p>需求:编写正则表达式匹配手机号 第一位:只能1 开头,第二位:3 4 5 7 8,长度:11位</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">static</span> <span class="cm-variable-3">void</span> <span class="cm-def">teleChk</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">telephone</span>) {<span class="cm-tab"> </span><span class="cm-tab"> </span><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">print</span>(<span class="cm-variable">telephone</span><span class="cm-operator">+</span><span class="cm-string">":"</span><span class="cm-variable">＋</span>(<span class="cm-variable">telephone</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"0\\d{2,3}-[1-9]\\d{6,7}"</span>)<span class="cm-operator">?</span><span class="cm-string">"Valid"</span>:<span class="cm-string">"Invalid"</span>));}</span></pre></div></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 68px;"></div></div></div></pre><p>需求:编写正则表达式匹配固话 形式 区号-主机号 区号首位是0,长度3- 4位 主机号:首位非0,长度7-8位</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">static</span> <span class="cm-variable-3">void</span> <span class="cm-def">phoneChk</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">phone</span>) {</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">print</span>(<span class="cm-variable">phone</span><span class="cm-operator">+</span><span class="cm-string">":"</span><span class="cm-variable">＋</span>(<span class="cm-variable">phone</span>.<span class="cm-variable">matches</span>(<span class="cm-string">"1[3578]\\d{9}"</span>)<span class="cm-operator">?</span><span class="cm-string">"Valid"</span>:<span class="cm-string">"Invalid"</span>));}</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 45px;"></div></div></div></pre><h5><a name='header-c654' class='md-header-anchor '></a>2.2.2 切割</h5><p>需求:字符串各个字符之间多个空格,需分割字符</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">static</span> <span class="cm-variable-3">void</span> <span class="cm-def">splitWd</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">ran</span>){</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-tab"> </span> <span class="cm-variable-3">String</span>[] <span class="cm-variable">res</span><span class="cm-operator">=</span><span class="cm-variable">ran</span>.<span class="cm-variable">split</span>(<span class="cm-string">" +"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-tab"> </span> <span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-variable">ran</span><span class="cm-operator">+</span><span class="cm-variable">Arrays</span>.<span class="cm-variable">toString</span>(<span class="cm-variable">res</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-tab"> </span>}</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 92px;"></div></div></div></pre><p>需求:根据重叠词进行切割 </p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">static</span> <span class="cm-variable-3">void</span> <span class="cm-def">splitDupWd</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">dupwd</span>){</span></pre></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-tab"> </span><span class="cm-tab"> </span><span class="cm-variable-3">String</span>[] <span class="cm-variable">resp</span><span class="cm-operator">=</span><span class="cm-variable">dupwd</span>.<span class="cm-variable">split</span>(<span class="cm-string">"(.)\\1+"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-tab"> </span><span class="cm-tab"> </span><span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-variable">dupwd</span><span class="cm-operator">+</span><span class="cm-variable">Arrays</span>.<span class="cm-variable">toString</span>(<span class="cm-variable">resp</span>));</span></pre><pre class=""><span style="padding-right: 0.1px;"><span class="cm-tab"> </span>}</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 92px;"></div></div></div></pre><p>()分组：如果正则的内容需要被复用,那么需要对正则的内容进行分组,分组的目的就是为了提高正则的复用性。</p><p>组号不能指定,组号从1开始</p><p>例((A)(B(C))) 组1:((A)(B(C))) 组2 (A) 组3 (B(C)) 组4 (C)</p><h5><a name='header-c667' class='md-header-anchor '></a>2.2.3 替换</h5><p>需求:去除文本中的广告电话</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">static</span> <span class="cm-variable-3">void</span> <span class="cm-def">replaceWd</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">org</span>)</span></pre></div><pre class=""><span style="padding-right: 0.1px;">{</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable-3">String</span> <span class="cm-variable">reg</span> <span class="cm-operator">=</span> <span class="cm-string">"1[3,4,5,7,8][0-9]{9}"</span>;</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable-3">String</span> <span class="cm-variable">ret</span> <span class="cm-operator">=</span> <span class="cm-variable">org</span>.<span class="cm-variable">replaceAll</span>(<span class="cm-variable">reg</span>, <span class="cm-string">"****"</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-variable">ret</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 134px;"></div></div></div></pre><p>需求:还原重复输入的话l如需要在方法正则的外部引用组内容,那么使用 “$组号”</p><h5><a name='header-c673' class='md-header-anchor '></a>2.2.4 查找</h5><p>典型调用顺序 </p><p>Pattern p= Pattern.compile(“正则” ) </p><p>Matcher m = p.matcher(“aaaab”)</p><p>查找需要的对象</p><ol><li>Pattern </li><li>Matcher </li></ol><p>匹配器要使用的方法</p><ol><li>find() 通知匹配器去查找,查找符合规则的字串</li><li>group() 获取符合规则的字符串</li></ol><p>需求：查找字符序列中长度为3的单词</p><pre class="md-fences md-end-block" lang="java"> <div class="CodeMirror cm-s-inner CodeMirror-wrap"><div style="overflow: hidden; position: relative; width: 3px; height: 0px; top: 0px; left: 4px;"></div><div class="CodeMirror-hscrollbar" style="left: 0px;"><div style="height: 100%; min-height: 1px; width: 0px;"></div></div><div class="CodeMirror-vscrollbar"><div style="min-width: 1px; height: 0px;"></div></div><div class="CodeMirror-scrollbar-filler"></div><div class="CodeMirror-gutter-filler"></div><div class="CodeMirror-scroll" tabindex="-1"><div class="CodeMirror-sizer" style="margin-left: 0px; min-height: 0px;"><div style="position: relative; top: 0px;"><div class="CodeMirror-lines"><div style="position: relative; outline: none;"><div class="CodeMirror-measure"><pre><span>xxxxxxxxxx</span></pre></div><div class="CodeMirror-measure"></div><div style="position: relative; z-index: 1;"></div><div class="CodeMirror-code"><div class="CodeMirror-activeline" style="position: relative;"><div class="CodeMirror-activeline-background CodeMirror-linebackground"></div><pre class=""><span style="padding-right: 0.1px;"><span class="cm-keyword">public</span> <span class="cm-keyword">static</span> <span class="cm-variable-3">void</span> <span class="cm-def">findWd2</span>(<span class="cm-variable-3">String</span> <span class="cm-variable">org</span>)</span></pre></div><pre class=""><span style="padding-right: 0.1px;">{</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable-3">String</span> <span class="cm-variable">reg</span> <span class="cm-operator">=</span> <span class="cm-string">"\\b[a-zA-Z]{3}\\b"</span>;</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable">Pattern</span> <span class="cm-variable">p</span> <span class="cm-operator">=</span> <span class="cm-variable">Pattern</span>.<span class="cm-variable">compile</span>(<span class="cm-variable">reg</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable">Matcher</span> <span class="cm-variable">m</span> <span class="cm-operator">=</span> <span class="cm-variable">p</span>.<span class="cm-variable">matcher</span>(<span class="cm-variable">org</span>);</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-keyword">while</span>(<span class="cm-variable">m</span>.<span class="cm-variable">find</span>())</span></pre><pre class=""><span style="padding-right: 0.1px;"> {</span></pre><pre class=""><span style="padding-right: 0.1px;"> <span class="cm-variable">System</span>.<span class="cm-variable">out</span>.<span class="cm-variable">println</span>(<span class="cm-variable">m</span>.<span class="cm-variable">group</span>());</span></pre><pre class=""><span style="padding-right: 0.1px;"> }</span></pre><pre class=""><span style="padding-right: 0.1px;">}</span></pre></div></div></div></div></div><div style="position: absolute; height: 30px; width: 1px; top: 0px;"></div><div class="CodeMirror-gutters" style="display: none; height: 224px;"></div></div></div></pre><p>\b代表单词边界,不匹配任何字符 用group方法时,一定先要调用find方法</p><p>版权声明：本文为复旦nlp组施展根据课堂内容整理的原创文章，转载请注明出处。</p></div>
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