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在Groovy中使用字符串

chengbinbbs

chengbinbbs

2009-06-15

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Groovy支持两种类型字符串：一般的Java字符串，它是java.lang.String的实例；和GStrings，它是groovy.lang.GString的实例，并且允许文本中包含占位符。GStrings并不是String的子类，因为String类是最终类（final class）不能被继承。然而，GString与一般的字符串一样，因为Groovy能将GStrings转型为Java strings。

GString 适用于编写模板代码（templating），因为您必须动态构建字符串（GStrings are useful in templating situations where you have to build your string dynamicly）。以下的清单给出了一个例子。

使用GStrings：

<ol class="dp-j">
<li class="alt"><span><span>firstWord = </span><span class="string"><font color="#0000ff">'Hello'</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span>secondWord = </span><span class="string"><font color="#0000ff">'dlroW'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>println  </span><span class="string"><font color="#0000ff">"$firstWord ${secondWord.reverse()}"</font></span><span> </span>
</li>
</ol>

结果如下：

<ol class="dp-xml"><li class="alt"><span><span>Hello World </span></span></li></ol>

GStrings不同于Java strings在于它们允许以${..}的语法嵌入变量。如果一个字符串由双引号或三重引号括起来，并且包含一个非转义符（unescaped）$，它必定是groovy.lang.GString的一个实例；否则，就是java.lang.String的一个实例。

${..}里可以包含任意有效的Groovy表达式，包括方法调用或变量名。只有调用GString的toString方法时（例如，把结果输出到控制台），${..}表达式才被求值。

Groovy支持的另一种字符串便是java.lang.String。然而，GDK还是动态注入许多帮助方法，使其易于应用。

以下的例子展示了在Groovy中声明一个字符串的不同方式：

<ol class="dp-j">
<li class="alt"><span><span>s1 = </span><span class="string"><font color="#0000ff">"Hello \"World\" "</font></span><span> </span><span class="comment"><font color="#008200">//Escape double quotes，转义双引号 </font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span>s2 = </span><span class="string"><font color="#0000ff">'Hello "World" '</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s1 == s2  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>s3 = </span><span class="string"><font color="#0000ff">'Hello \'World\' '</font></span><span> </span><span class="comment"><font color="#008200">//Escape single quotes，转义单引号 </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>s4 = </span><span class="string"><font color="#0000ff">"Hello 'World' "</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s3 == s4  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> String(</span><span class="string"><font color="#0000ff">'Hello World'</font></span><span>) == </span><span class="string"><font color="#0000ff">"Hello World"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>def s = [</span><span class="string"><font color="#0000ff">'h'</font></span><span>,</span><span class="string"><font color="#0000ff">'e'</font></span><span>,</span><span class="string"><font color="#0000ff">'l'</font></span><span>,</span><span class="string"><font color="#0000ff">'l'</font></span><span>,</span><span class="string"><font color="#0000ff">'o'</font></span><span>] as </span><span class="keyword"><strong><font color="#006699">char</font></strong></span><span>[]  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> String(s) == </span><span class="string"><font color="#0000ff">'hello'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> String(s,</span><span class="number"><font color="#c00000">0</font></span><span>,</span><span class="number"><font color="#c00000">4</font></span><span>) == </span><span class="string"><font color="#0000ff">'hell'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>s.eachWithIndex{ch,index -> </span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> ch == s[index]}  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello'</font></span><span>.toCharArray() == [</span><span class="string"><font color="#0000ff">'h'</font></span><span>,</span><span class="string"><font color="#0000ff">'e'</font></span><span>,</span><span class="string"><font color="#0000ff">'l'</font></span><span>,</span><span class="string"><font color="#0000ff">'l'</font></span><span>,</span><span class="string"><font color="#0000ff">'o'</font></span><span>]  </span>
</li>
<li class=""><span> </span></li>
<li class="alt"><span>   </span></li>
</ol>

常用的转义符：

<ol class="dp-j">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'\t'</font></span><span> == </span><span class="string"><font color="#0000ff">'\011'</font></span><span>    </span><span class="comment"><font color="#008200">//Tab，Tab键 </font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'\n'</font></span><span> == </span><span class="string"><font color="#0000ff">'\012'</font></span><span>    </span><span class="comment"><font color="#008200">//New line，换行符 </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'\r'</font></span><span> == </span><span class="string"><font color="#0000ff">'\015'</font></span><span>    </span><span class="comment"><font color="#008200">//Carriage return，回车 </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'\n'</font></span><span> == </span><span class="string"><font color="#0000ff">""</font></span><span>"  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="string"><font color="#0000ff">""</font></span><span>" </span><span class="comment"><font color="#008200">//Spanning multiple lines，跨越多行 </font></span><span> </span>
</li>
</ol>

对象的字符串表示：

<ol class="dp-j">
<li class="alt"><span><span>def object = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> Object()  </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> String.valueOf(object) == object.toString() </span><span class="comment"><font color="#008200">//Objects  </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> String.valueOf(</span><span class="keyword"><strong><font color="#006699">true</font></strong></span><span>) == </span><span class="keyword"><strong><font color="#006699">true</font></strong></span><span>.toString() </span><span class="comment"><font color="#008200">//Booleans  </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> String.valueOf(</span><span class="string"><font color="#0000ff">'a'</font></span><span>) == </span><span class="string"><font color="#0000ff">'a'</font></span><span>.toString() </span><span class="comment"><font color="#008200">//Characters  </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> String.valueOf(</span><span class="number"><font color="#c00000">1</font></span><span>) == </span><span class="number"><font color="#c00000">1</font></span><span>.toString() </span><span class="comment"><font color="#008200">//Numbers </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> String.valueOf([a:</span><span class="number"><font color="#c00000">1</font></span><span>,b:</span><span class="number"><font color="#c00000">2</font></span><span>]) == [a:</span><span class="number"><font color="#c00000">1</font></span><span>,b:</span><span class="number"><font color="#c00000">2</font></span><span>].toString() </span><span class="comment"><font color="#008200">//Collections </font></span><span> </span>
</li>
</ol>

字符串长度：

<ol class="dp-j">
<li class="alt"><span><span>s = </span><span class="string"><font color="#0000ff">"Hello World"</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.size() == </span><span class="number"><font color="#c00000">11</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.size() == s.length()  </span>
</li>
</ol>

填充（pad）字符串：

<ol class="dp-j">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'Hello'</font></span><span>.padRight(</span><span class="number"><font color="#c00000">7</font></span><span>,</span><span class="string"><font color="#0000ff">'*'</font></span><span>) == </span><span class="string"><font color="#0000ff">'Hello**'</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'Hello'</font></span><span>.padLeft(</span><span class="number"><font color="#c00000">7</font></span><span>,</span><span class="string"><font color="#0000ff">'*'</font></span><span>) == </span><span class="string"><font color="#0000ff">'**Hello'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'Hello'</font></span><span>.center(</span><span class="number"><font color="#c00000">9</font></span><span>,</span><span class="string"><font color="#0000ff">'*'</font></span><span>) == </span><span class="string"><font color="#0000ff">'**Hello**'</font></span><span> </span>
</li>
</ol>

分解字符串：

<ol class="dp-j">
<li class="alt"><span><span>s = </span><span class="string"><font color="#0000ff">"The quick brown fox jumps over the lazy dog"</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.tokenize() == [</span><span class="string"><font color="#0000ff">'The'</font></span><span>,</span><span class="string"><font color="#0000ff">'quick'</font></span><span>,</span><span class="string"><font color="#0000ff">'brown'</font></span><span>,</span><span class="string"><font color="#0000ff">'fox'</font></span><span>,</span><span class="string"><font color="#0000ff">'jumps'</font></span><span>,</span><span class="string"><font color="#0000ff">'over'</font></span><span>,</span><span class="string"><font color="#0000ff">'the'</font></span><span>,</span><span class="string"><font color="#0000ff">'lazy'</font></span><span>,</span><span class="string"><font color="#0000ff">'dog'</font></span><span>]  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.tokenize() == </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> StringTokenizer(s).collect{it}  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>s1 = </span><span class="string"><font color="#0000ff">"The,quick*brown*fox,*jumps*over*the*lazy*dog"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s1.tokenize(</span><span class="string"><font color="#0000ff">',*'</font></span><span>) == s.tokenize()  </span>
</li>
</ol>

查询字符串：

<ol class="dp-j">
<li class="alt"><span><span>alphabets = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> String(</span><span class="string"><font color="#0000ff">'a'</font></span><span> .. </span><span class="string"><font color="#0000ff">'z'</font></span><span> as </span><span class="keyword"><strong><font color="#006699">char</font></strong></span><span>[])  </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.find{it > </span><span class="string"><font color="#0000ff">'f'</font></span><span>} == </span><span class="string"><font color="#0000ff">'g'</font></span><span> </span><span class="comment"><font color="#008200">//First one found </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.findAll{it > </span><span class="string"><font color="#0000ff">'f'</font></span><span>} == </span><span class="string"><font color="#0000ff">'g'</font></span><span> .. </span><span class="string"><font color="#0000ff">'z'</font></span><span class="comment"><font color="#008200">//ALl found </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.findIndexOf{ it > </span><span class="string"><font color="#0000ff">'f'</font></span><span>} == alphabets.indexOf(</span><span class="string"><font color="#0000ff">'g'</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.every {it > </span><span class="string"><font color="#0000ff">'A'</font></span><span>}  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.any{it <span class="string"><font color="#0000ff">'c'</font></span><span>}  </span></span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.startsWith(</span><span class="string"><font color="#0000ff">'abc'</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.endsWith(</span><span class="string"><font color="#0000ff">'xyz'</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.contains(</span><span class="string"><font color="#0000ff">'def'</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.indexOf(</span><span class="string"><font color="#0000ff">'c'</font></span><span>) == </span><span class="number"><font color="#c00000">2</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.indexOf(</span><span class="string"><font color="#0000ff">'d'</font></span><span>) == alphabets.lastIndexOf(</span><span class="string"><font color="#0000ff">'d'</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> alphabets.count(</span><span class="string"><font color="#0000ff">'a'</font></span><span>) == </span><span class="number"><font color="#c00000">1</font></span><span> </span>
</li>
</ol>

替换字符串：

<ol class="dp-j">
<li class="alt"><span><span>s = </span><span class="string"><font color="#0000ff">"Hello"</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.replace(</span><span class="string"><font color="#0000ff">'H'</font></span><span>,</span><span class="string"><font color="#0000ff">'Y'</font></span><span>) == </span><span class="string"><font color="#0000ff">'Yello'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.replace(</span><span class="string"><font color="#0000ff">'l'</font></span><span>,</span><span class="string"><font color="#0000ff">'p'</font></span><span>) == </span><span class="string"><font color="#0000ff">'Heppo'</font></span><span> </span>
</li>
</ol>

字符串反转：

<ol class="dp-j">
<li class="alt"><span><span>s = </span><span class="string"><font color="#0000ff">'mirror'</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> s.reverse() == </span><span class="string"><font color="#0000ff">'rorrim'</font></span><span> </span>
</li>
</ol>

字符串操作符：

<ol class="dp-j">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello'</font></span><span> + </span><span class="string"><font color="#0000ff">' world'</font></span><span> - </span><span class="string"><font color="#0000ff">'l'</font></span><span> == </span><span class="string"><font color="#0000ff">'helo world'</font></span><span> </span><span class="comment"><font color="#008200">//Subtracts at most one l </font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> (</span><span class="string"><font color="#0000ff">'Today is Sunday'</font></span><span> - </span><span class="string"><font color="#0000ff">'Sunday'</font></span><span>).trim() == </span><span class="string"><font color="#0000ff">'Today is'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello '</font></span><span> * </span><span class="number"><font color="#c00000">2</font></span><span> == </span><span class="string"><font color="#0000ff">'hello hello '</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt"><span>def empty = []  </span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'abc'</font></span><span>.each{empty <span class="string"><font color="#0000ff">'abc'</font></span><span> </span></span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'abc'</font></span><span>.next() == </span><span class="string"><font color="#0000ff">'abd'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'abc'</font></span><span>.previous() == </span><span class="string"><font color="#0000ff">'abb'</font></span><span> </span>
</li>
</ol>

下标操作符：

<ol class="dp-j">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello'</font></span><span>[</span><span class="number"><font color="#c00000">1</font></span><span>] == </span><span class="string"><font color="#0000ff">'e'</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello'</font></span><span>[</span><span class="number"><font color="#c00000">2</font></span><span>..</span><span class="string"><font color="#0000ff">'hello'</font></span><span>.size() - </span><span class="number"><font color="#c00000">1</font></span><span>] == </span><span class="string"><font color="#0000ff">'llo'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello'</font></span><span>[</span><span class="number"><font color="#c00000">0</font></span><span>,</span><span class="number"><font color="#c00000">2</font></span><span>,</span><span class="number"><font color="#c00000">4</font></span><span>] == </span><span class="string"><font color="#0000ff">'hlo'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'hello'</font></span><span>[-</span><span class="number"><font color="#c00000">4</font></span><span>,-</span><span class="number"><font color="#c00000">2</font></span><span>] == </span><span class="string"><font color="#0000ff">'el'</font></span><span> </span>
</li>
</ol>

字符串比较：

<ol class="dp-j">
<li class="alt"><span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'a'</font></span><span> <span class="string"><font color="#0000ff">'b'</font></span><span> </span></span><li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'a'</font></span><span> > </span><span class="string"><font color="#0000ff">'A'</font></span><span> </span>
</li></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'a'</font></span><span>.compareTo(</span><span class="string"><font color="#0000ff">'b'</font></span><span>) == -</span><span class="number"><font color="#c00000">1</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> </span><span class="string"><font color="#0000ff">'a'</font></span><span>.compareToIgnoreCase(</span><span class="string"><font color="#0000ff">'A'</font></span><span>) == </span><span class="number"><font color="#c00000">0</font></span><span> </span>
</li>
</ol>

寻找最大值和最小值：

<ol class="dp-j">
<li class="alt"><span><span>Collections.max(</span><span class="string"><font color="#0000ff">'abcdeF'</font></span><span>.toList()) == </span><span class="string"><font color="#0000ff">'e'</font></span><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> Collections.max(</span><span class="string"><font color="#0000ff">'abcdeF'</font></span><span>.toList(), String.CASE_INSENSITIVE_ORDER) == </span><span class="string"><font color="#0000ff">'F'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> Collections.min([</span><span class="string"><font color="#0000ff">'abc'</font></span><span>,</span><span class="string"><font color="#0000ff">'abd'</font></span><span>,</span><span class="string"><font color="#0000ff">'abe'</font></span><span>]) == </span><span class="string"><font color="#0000ff">'abc'</font></span><span>      </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> Collections.min([</span><span class="string"><font color="#0000ff">'Abc'</font></span><span>,</span><span class="string"><font color="#0000ff">'aBd'</font></span><span>,</span><span class="string"><font color="#0000ff">'abE'</font></span><span>], String.CASE_INSENSITIVE_ORDER) == </span><span class="string"><font color="#0000ff">'Abc'</font></span><span> </span>
</li>
</ol>

StringBuffers和StringBuilders是可变的，允许字符串改变。StringBuilder不是线程安全的，因此处理速度要比StringBuffers快。

<ol class="dp-j">
<li class="alt"><span><span>def sb = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> StringBuffer(</span><span class="string"><font color="#0000ff">'Hello World'</font></span><span>)  </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == </span><span class="string"><font color="#0000ff">'Hello World'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>sb.length = </span><span class="number"><font color="#c00000">5</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == </span><span class="string"><font color="#0000ff">'Hello'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.substring(</span><span class="number"><font color="#c00000">0</font></span><span>,</span><span class="number"><font color="#c00000">2</font></span><span>) == </span><span class="string"><font color="#0000ff">'He'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="comment"><font color="#008200">//Use </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="comment"><font color="#008200">//Using + to append to a StringBuffer will return a String </font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>sb = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> StringBuffer(</span><span class="string"><font color="#0000ff">"Hello"</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb + </span><span class="string"><font color="#0000ff">' World'</font></span><span> in java.lang.String  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb <span class="string"><font color="#0000ff">' World'</font></span><span> in java.lang.StringBuffer  </span></span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == (</span><span class="string"><font color="#0000ff">"Hello World"</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.append(</span><span class="string"><font color="#0000ff">", Groovy rocks"</font></span><span>).toString() == </span><span class="string"><font color="#0000ff">"Hello World, Groovy rocks"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.leftShift(</span><span class="string"><font color="#0000ff">". Doesn't?"</font></span><span>).toString() == </span><span class="string"><font color="#0000ff">"Hello World, Groovy rocks. Doesn't?"</font></span><span> </span>
</li>
</ol>

您也可以对StringBuffer或StringBuilder使用下标，如：

<ol class="dp-j">
<li class="alt"><span><span>sb = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> StringBuffer(</span><span class="string"><font color="#0000ff">"abcdefg"</font></span><span>)  </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb[</span><span class="number"><font color="#c00000">0</font></span><span>] == </span><span class="string"><font color="#0000ff">'a'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb[</span><span class="number"><font color="#c00000">2</font></span><span>..</span><span class="number"><font color="#c00000">4</font></span><span>] == </span><span class="string"><font color="#0000ff">'cde'</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb[</span><span class="number"><font color="#c00000">0</font></span><span>].</span><span class="keyword"><strong><font color="#006699">class</font></strong></span><span> == String  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb[-</span><span class="number"><font color="#c00000">6</font></span><span>..-</span><span class="number"><font color="#c00000">4</font></span><span>] == </span><span class="string"><font color="#0000ff">"bcd"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>sb[</span><span class="number"><font color="#c00000">0</font></span><span>..</span><span class="number"><font color="#c00000">2</font></span><span>] = </span><span class="string"><font color="#0000ff">"xyz"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == </span><span class="string"><font color="#0000ff">"xyzdefg"</font></span><span> </span>
</li>
</ol>

操作StringBuffers：

<ol class="dp-j">
<li class="alt"><span><span>sb = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> StringBuffer(</span><span class="string"><font color="#0000ff">"StringBuffers are mutable"</font></span><span>)  </span></span></li>
<li class=""><span> </span></li>
<li class="alt">
<span>sb.delete(sb.indexOf(</span><span class="string"><font color="#0000ff">" are mutable"</font></span><span>),sb.size())  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == </span><span class="string"><font color="#0000ff">"StringBuffers"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>sb.insert(sb.size(), </span><span class="string"><font color="#0000ff">" are mutable"</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == </span><span class="string"><font color="#0000ff">"StringBuffers are mutable"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>sb.replace(sb.indexOf(</span><span class="string"><font color="#0000ff">"StringBuffers"</font></span><span>), </span><span class="string"><font color="#0000ff">"StringBuffers"</font></span><span>.size(), </span><span class="string"><font color="#0000ff">"StringBuilders"</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> sb.toString() == </span><span class="string"><font color="#0000ff">"StringBuilders are mutable"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>def string = </span><span class="keyword"><strong><font color="#006699">new</font></strong></span><span> String(sb)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>def string2 = string.replaceAll(</span><span class="string"><font color="#0000ff">"StringBuilders"</font></span><span>, </span><span class="string"><font color="#0000ff">"StringBuffers"</font></span><span>)  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span></span><span class="keyword"><strong><font color="#006699">assert</font></strong></span><span> string2 == </span><span class="string"><font color="#0000ff">"StringBuffers are mutable"</font></span><span> </span>
</li>
<li class=""><span> </span></li>
<li class="alt"><span>   </span></li>
</ol>

正如您看到的，GDK在java.lang.String，java.lang.StringBuffer和java.lang.StringBuilder基础上添加了很多实用的方法。前面的例子只讨论部分方法，因此推荐您查看String的API文档，http://groovy.codehaus.org/groovy-jdk/java/lang/String.html；StringBuffer, http://groovy.codehaus.org/groovy-jdk/java/lang/StringBuffer.html; StringBuilder, http://groovy.codehaus.org/groovy-jdk/java/lang/StringBuilder.html。

在Groovy中使用字符串时，需要注意以下几点：

与Java一样，Groovy中的字符串也是不可变的（即只读的）。欲改变字符串值需使用StringBuffer或StringBuilder。

Groovy中，如果字符串如果由单引号括起来，或者由双引号或三重引号括起来但没有非转义的美元符号（$），那么该字符串是java.lang.String的一个实例。您可使用JDK中任意字符串方法。另外，GDK动态注入额外的实用方法到String类。

由于Groovy会自动转型为String类，您可以在任何时候使用GStrings。

字符串可被单引号，双引号或者三重引号括起来。其中，三重引号可直接跨越数行并且输出中仍包含回车符、制表符和空格符。

Groovy使用size方法来查询一个字符串，StringBuffer或StringBuilder的长度，与查询一个集合的长度相统一。

某些字符串方法接受闭包，它明确说明需要满足的条件，例如，find，findAll，findIndexOf，every和any。这些方法都是由GDK动态注入到java.lang.Object中的。

您可以使用collect，each或者eachWithIndex方法遍历字符串，而且这些方法也属于java.lang.Object的一部分。

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定义了 Runnable 接口，并在根类 Object 中提供了 wait/notify 方法，还有 synchronized 关键字的支持。我们常说实现多线程的方式有两种：继承 Thread类和实现 Runnable接口，实质上工作者线程执行的都是 Ru

春天花会开 2016-11-01

管理密码集中化

并把取出的密码集中保存到唯一的properties格式的文件中。完整的项目代码和资源请查看附件。// Set main property to name of Groovy script class.// Set classpath for running

无聊找点事做 2015-03-28
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