将整个单词与字符串中的前导或尾随特殊符号(例如美元)匹配 [英] Matching a whole word with leading or trailing special symbols like dollar in a string

问题描述

我可以使用 Matcher.quoteReplacement替换美元符号.我可以通过添加边界字符来替换单词:

I can replace dollar signs by using Matcher.quoteReplacement. I can replace words by adding boundary characters:

from = "\\b" + from + "\\b"; 
outString = line.replaceAll(from, to);

但是我似乎无法将它们结合起来用美元符号代替单词.

But I can't seem to combine them to replace words with dollar signs.

这是一个例子.我正在尝试将" $ temp4 "(不是 $ temp40 )替换为" register1 ".

Here's an example. I am trying to replace "$temp4" (NOT $temp40) with "register1".

        String line = "add, $temp4, $temp40, 42";
        String to = "register1";
        String from = "$temp4";
        String outString;


        from = Matcher.quoteReplacement(from);
        from = "\\b" + from + "\\b";  //do whole word replacement

        outString = line.replaceAll(from, to);
        System.out.println(outString);

输出

"add, $temp4, $temp40, 42"

如何获取它来替换$ temp4和仅替换$ temp4?

How do I get it to replace $temp4 and only $temp4?

推荐答案

使用明确的单词边界，(?<！\ w)和(?！\ w)，而不是与上下文相关的 \ b :

Use unambiguous word boundaries, (?<!\w) and (?!\w), instead of \b that are context dependent:

from = "(?<!\\w)" + Pattern.quote(from) + "(?!\\w)";

请参见 正则表达式演示 .

如果当前位置和(?!\ w)是一个否定的超前查询，如果当前位置右侧紧邻有一个非单词char，则匹配失败.要避免 from 变量中的任何特殊字符，必须使用 Pattern.quote(from).

The (?<!\w) is a negative lookbehind that fails the match if there is a non-word char immediately to the left of the current location and (?!\w) is a negative lookahead that fails the match if there is a non-word char immediately to the right of the current location. The Pattern.quote(from) is necessary to escape any special chars in the from variable.

请参见 Java演示:

String line = "add, $temp4, $temp40, 42";
String to = "register1";
String from = "$temp4";
String outString;

from = "(?<!\\w)" + Pattern.quote(from) + "(?!\\w)";

outString = line.replaceAll(from, to);
System.out.println(outString);
// => add, register1, $temp40, 42

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