正则表达式中的单词边界是什么? [英] What is a word boundary in regex?

问题描述

我正在尝试使用正则表达式来匹配以空格分隔的数字.我找不到 (词边界")的精确定义.我曾假设 -12 将是一个整数词".(由 -?d+ 匹配)但似乎这不起作用.我很高兴知道 .

I'm trying to use regexes to match space-separated numbers. I can't find a precise definition of  ("word boundary"). I had assumed that -12 would be an "integer word" (matched by -?d+) but it appears that this does not work. I'd be grateful to know of ways of .

[我在 Java 1.6 中使用 Java 正则表达式]

[I am using Java regexes in Java 1.6]

示例:

Pattern pattern = Pattern.compile("\s*\b\-?\d+\s*");
String plus = " 12 ";
System.out.println(""+pattern.matcher(plus).matches());

String minus = " -12 ";
System.out.println(""+pattern.matcher(minus).matches());

pattern = Pattern.compile("\s*\-?\d+\s*");
System.out.println(""+pattern.matcher(minus).matches());

返回:

true
false
true

推荐答案

在大多数正则表达式方言中，单词边界是 w 和 W 之间的位置(非单词字符)，或者在字符串的开头或结尾，如果它以单词字符([0-9A-Za-z_])开头或结尾(分别).

A word boundary, in most regex dialects, is a position between w and W (non-word char), or at the beginning or end of a string if it begins or ends (respectively) with a word character ([0-9A-Za-z_]).

因此，在字符串 "-12" 中，它会匹配 1 之前或 2 之后.破折号不是单词字符.

So, in the string "-12", it would match before the 1 or after the 2. The dash is not a word character.

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