在Java中使用\b边界匹配器 [英] Use of \b Boundary Matcher In Java
问题描述
我正在阅读Oracle文档中的边界匹配器。我理解大部分内容，但我无法掌握 \b 边界匹配器。以下是文档中的示例。
I am reading Boundary Matcher from Oracle Documentation. I understand most of the part, but i am not able to grasp the \b Boundary Matcher. Here is the example from the documentation.
检查模式是否在单词边界开始和结束（而不是
到一个较长字符串中的子字符串），只需在两边使用\ b;例如
，\ bdog \ b
To check if a pattern begins and ends on a word boundary (as opposed to a substring within a longer string), just use \b on either side; for example, \bdog\b
输入你的正则表达式：\ bdog \b输入要搜索的输入字符串：狗玩
在院子里。我发现文本dog从索引4开始，到
索引7结束。
Enter your regex: \bdog\b Enter input string to search: The dog plays in the yard. I found the text "dog" starting at index 4 and ending at index 7.
输入你的正则表达式：\ bdog \b输入输入字符串到搜索：小狗
在院子里玩。找不到匹配项。要匹配
非字边界上的表达式，请改为使用\B：
Enter your regex: \bdog\b Enter input string to search: The doggie plays in the yard. No match found. To match the expression on a non-word boundary, use \B instead:
输入正则表达式：\ bdog \B输入输入字符串到搜索：狗
在院子里玩。找不到匹配。
Enter your regex: \bdog\B Enter input string to search: The dog plays in the yard. No match found.
输入您的正则表达式：\ bdog \B输入要搜索的输入字符串：小狗
在院子里播放。我发现文本dog从索引4开始，
从索引7开始。
Enter your regex: \bdog\B Enter input string to search: The doggie plays in the yard. I found the text "dog" starting at index 4 and ending at index 7.
简而言之，我不是能够理解\ b的工作。有人可以帮我描述它的用法，并帮助我理解这个例子。
In short, i am not able to understand the working of \b. Can someone help me describing its usage and help me understand this example.
谢谢
推荐答案
\b 是你可以称之为锚点的东西：它将匹配输入文本中的位置。
\b is what you can call an "anchor": it will match a position in the input text.
更具体地说， \b 将匹配输入文本中的每个位置：
More specifically, \b will match every position in the input text where:
- 没有前面的字符，后面的字符是单词字符（任何字母或数字，或下划线）;
- 没有后面的字符和前面的字符字符是单词字符;
- 前面的字符是单词字符，后面的字符不是;或
- 以下字符是单词字符，前面的字符不是。
- there is no preceding character and the following character is a word character (any letter or digit, or an underscore);
- there is no following character and the preceding character is a word character;
- the preceding character is a word character and the following character is not; or
- the following character is a word character and the preceding character is not.
For例如，文本我的狗吃中的正则表达式 dog \b 将匹配 g dog （这是一个单词字符），在下面的空格之前（不是）。
For instance, the regex dog\b in the text "my dog eats" will match the position immediately after the g of dog (which is a word character) and before the following space (which is not).
请注意，与所有锚点一样，它与位置匹配的事实意味着它不使用任何输入文本。
Note that like all anchors, the fact that it matches a position means that it does not consume any input text.
其他锚点是 ^ ， $ ，外观。
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