Java 如何用\替换字符串中的一个或多个\？

How to replace one or more \ in string with just \?

提问by Destructor

Consider the string,

考虑字符串，

this\is\a\new\string

The output should be:

输出应该是：

this\is\a\new\string

So basically one or more \character should be replaced with just one \. I tried the following:

所以基本上一个或多个\字符应该只替换为一个\. 我尝试了以下方法：

str = str.replace("[\]+","\")

but it was no use. The reason I used two \in [\\]+was because internally \is stored as \\. I know this might be a basic regex question, but I am able to replace one or more normal alphabets but not \character. Any help is really appreciated.

但没有用。我使用两个\in的原因[\\]+是因为内部\存储为\\. 我知道这可能是一个基本的正则表达式问题，但我可以替换一个或多个普通字母而不是\字符。任何帮助都非常感谢。

采纳答案by Pshemo

str.replace("[\\]+", "\")has few problems,

str.replace("[\\]+", "\")问题很少，

• replacedoesn't use regex (replaceAlldoes) so "[\\]"will represent [\]literal, not \nor \\(depending on what you think it would represent)
• even if it did accept regex "[\\]"would not be correct regex because \\]would escape ]so you would end up with unclosed character class [..
• it will not compile (your replacement String is not closed)

• replace不使用正则表达式（replaceAll确实）所以"[\\]"将代表[\]文字，而\不是\\（取决于你认为它代表什么）
• 即使它确实接受正则表达式"[\\]"也不是正确的正则表达式，因为\\]会转义，]因此您最终会得到未关闭的字符类[..
• 它不会编译（您的替换字符串未关闭）

It will not compile because \is start of escape sequence \Xwhere Xneeds to be either

它不会编译，因为它\是转义序列的开始\X，X需要是

• changed from being String special character to simple literal, like in your case \"will escape "to be literal (so you could print it for instance) instead of being start/end of String,
• changed from being normal character to be special one like in case of line separators \n\ror tabulations \t.

• 从字符串特殊字符更改为简单文字，就像在您的情况下\"将转义"为文字（例如，您可以打印它）而不是字符串的开始/结束，
• 从正常字符变为特殊字符，例如行分隔符\n\r或制表符\t。

Now we know that \is special and is used to escape other character. So what do you think we need to do to make \represent literal (when we want to print \). If you guessed that it needs to be escaped with another \then you are right. To create \literal we need to write it in String as "\\".

现在我们知道这\是特殊的，用于转义其他字符。那么你认为我们需要做什么来使\代表文字（当我们想要打印时\）。如果您猜测它需要与另一个转义，\那么您是对的。要创建\文字，我们需要将它写在 String as 中"\\"。

Since you know how to create String containing \literal (escaped \) you can start thinking about how to create your replacements.

既然您知道如何创建包含\文字（转义\）的字符串，您就可以开始考虑如何创建替换。

Regex which represents one or more \can look like

代表一个或多个的正\则表达式看起来像

\\+

\\+

But that is its native form, and we need to create it using String. I used \\here because in regex \is also special character (for instance \drepresents digits, not \literal followed by d) so it also needs to be escaped first to represent \literal. Just like in String we can escape it with another \.

但这是它的原生形式，我们需要使用 String 来创建它。我\\在这里使用\是因为在正则表达式中也是特殊字符（例如\d表示数字，而不是\文字后跟d）所以它也需要先转义以表示\文字。就像在 String 中一样，我们可以用另一个\.

So String representing this regex will need to be written as

所以表示这个正则表达式的字符串需要写成

"\\\\+"(we escaped \twice, once in regex \\+and once in string)

"\\\\+"（我们转义了\两次，一次在正则表达式中\\+，一次在字符串中）

You can use it as first argument of replaceAll(because replaceas mentioned earlier doesn't accept regex).

您可以将其用作replaceAll( 因为replace如前所述不接受正则表达式) 的第一个参数。

Now last problem you will face is second argument of replaceAllmethod. If you write

现在您将面临的最后一个问题是replaceAll方法的第二个参数。如果你写

replaceAll("\\\\+", "\\")

replaceAll("\\\\+", "\\")

and it will find match for regex you will see exception

它会找到正则表达式的匹配，你会看到异常

java.lang.IllegalArgumentException: character to be escaped is missing

It is because in replacementpart (second argument in replaceAllmethod) we can also use special formula $xwhich represents current match from group with index x. So to be able to escape $into literal we need some escape mechanism, and again \was used here for that purpose. So \is also special in replacement partof our method.
So again to create \literal we need to escape it with another \, and string literal representing expression \\is "\\\\".

这是因为replacement部分（replaceAll方法中的第二个参数）我们还可以使用特殊公式$x来表示来自具有 index 的组的当前匹配x。因此，为了能够转义$为字面意思，我们需要一些转义机制，\此处再次用于此目的。所以\我们方法的替换部分也很特别。
所以再次创建\文字我们需要用另一个转义它\，并且字符串文字表示表达式\\is "\\\\"。

But lets get back to earlier exception: message "character to be escaped is missing" refers to Xpart of \Xformula (X is character we want to be escaped). Problem is that earlier your replacement "\\"represented only \part, so this method expected either $to create \$, or \\to create \literal. So valid replacements would be "\\$or "\\\\".

但是让我们回到之前的异常：消息“要转义的字符丢失”指的X是\X公式的一部分（X 是我们想要转义的字符）。问题是之前你的替换"\\"只代表了\一部分，所以这个方法期望要么$创建\$，要么\\创建\文字。所以有效的替换是"\\$or "\\\\"。

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To make things work you need to write your replacing method as

为了使事情工作，您需要将替换方法编写为

str = str.replaceAll("\\+", "\\")

回答by anubhava

You can use:

您可以使用：

str = str.replace("\\", "\");

Remember that String#replacedoesn't take a regex.

请记住，这String#replace不需要正则表达式。

回答by JLRishe

When writing regular expressions, you typically need to double-escape backslashes. So you would do this:

编写正则表达式时，您通常需要对反斜杠进行双重转义。所以你会这样做：

str = str.replaceAll("\\+", "\\");

回答by Evgeniy Dorofeev

try this

尝试这个

str = str.replaceAll("\\+", "\\");

回答by Micha F.

I'd use Matcher.quoteReplacement()and String.replaceAll()here.

我会在这里使用Matcher.quoteReplacement()和String.replaceAll()。

Like this:

像这样：

String s;
[...]
s = s.replaceAll("\\+", Matcher.quoteReplacement("\"));