如何在regex中为Java String使用开始和结束标记？ [英] How to use beginning and endline markers in regex for Java String?

问题描述

为什么以下内容没有更改Android中的文字？

Why doesn't the following change the text for me in Android?

String content = "test\n=test=\ntest";
content = content.replaceAll("^=(.+)=$", "<size:large>$1</size:large>")

它返回原始值而不做任何更改。我希望它用替换中间 = test = < size：large> test< / size：large>

It returns the original value with no changes. I would expect it to replace the middle =test= with <size:large>test</size:large>

我在这里缺少什么？

编辑：好的，我明白为什么 ^ 和 $ 不起作用。关键是我需要在行的开头和结尾都匹配文本的东西，例如：一行只包含= some text =。由于以下原因，大多数答案都不充分：

Okay, I understand why ^ and $ don't work. The point is that I need something that matches text both at the beginning and end of a line, e.g. a line that contains only "=some text=". Most of the answers given aren't sufficient, for the following reasons:

=（。+）= 不与行结尾有任何关系，因此在其中匹配任何不是并排的 = 的行。

=(.+)= doesn't have anything to do with line endings, so matches any line with two = in it that are not side by side.

。* =（。+）=。* 匹配整行，但与上一行有相同的问题

.*=(.+)=.* matches the whole line, but has the same problem as the previous

\ n =（。+）= \ n 靠近，但不会连续匹配两行（例如 test\\\
= test = \ n = test = \\\ lt ）它也不会匹配第一行或最后一行的实例

\n=(.+)=\n gets closer, but won't match two lines in a row (e.g. test\n=test=\n=test=\ntest) It also won't match an instance on the first or last line

（？< = \ n）=（。+）=（？= \ n）几乎可以正常工作，但再次与实例不匹配在第一行或最后一行

(?<=\n)=(.+)=(?=\n) almost works, but again won't match an instance on the first or last line

（？<！。）=（。+）=（？！。）是唯一一个看起来实际上匹配以 = 开头和结尾的每一行，但是$ 1包含替换字符串和原始字符串。

(?<!.)=(.+)=(?!.) is the only one that seems will actually match every line that starts and ends with =, for example, but $1 contains both the replacement and the original string.

content = content.replaceAll（（？< =（ \\ n | ^））=（。+）=（？=（\ n | $）），< size：large> $ 2< / size：large>）; 是唯一可以实际应该做的事情的答案。

content = content.replaceAll("(?<=(\n|^))=(.+)=(?=(\n|$))", "<size:large>$2</size:large>"); is the only answer that seems to actually do what it should.

推荐答案

如果打开多线模式，原始正则表达式可以正常工作使用（？m）：

Your original regex works fine if you turn on multiline mode, using (?m):

content = content.replaceAll("(?m)^=(.+)=$", "<size:large>$1</size:large>");

现在 ^ 和 $ 确实在行边界处匹配。

Now ^ and $ do indeed match at line boundaries.

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