Java Regex Word边界 [英] Java Regex Word Boundaries

问题描述

我有以下代码，该代码旨在查找单词"is"，但不是在另一个字符串中时才查找，因此单词"this"不应返回匹配项，因此我使用\ b.但是以下代码找不到匹配项，我无法弄清楚为什么?

Hi I have the following code which is meant to find the word "is" but not when it is within another string so the word "this" should not return a match so I use \b. But the following code does not find a match and I cant figure out why?

public static void main(String[] args) {
    String a = "This island is beautiful.";
    Pattern p = Pattern.compile("\bis\b");
    Matcher m = p.matcher(a);

    while(m.find()){

        System.out.println(a.substring(m.start(), m.end()));
    }

}

推荐答案

对其进行两次转义:

Pattern p = Pattern.compile("\\bis\\b");

Java中的正则表达式要求您加倍转义某些特殊的正则表达式符号，一个转义为Java，另一个转义为基础正则表达式引擎.

Regex in Java requires you to doubly escape certain special regex symbols, one escaping for Java and another for underlying regex engine.

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