java 如何用单斜杠替换特殊字符

How to replace a special character with single slash

提问by swati

I have a question about strings in Java. Let's say, I have a string like so:

我有一个关于 Java 字符串的问题。比方说，我有一个像这样的字符串：

String str = "The . startup trace ?state is info?";

As the string contains the special character like "?"I need the string to be replaced with "\?"as per my requirement. How do I replace special characters with "\"? I tried the following way.

由于字符串包含特殊字符，就像"?"我需要"\?"根据我的要求替换字符串一样。如何用 替换特殊字符"\"？我尝试了以下方法。

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

But it gives a compilation error. Then I tried the following:

但它给出了编译错误。然后我尝试了以下方法：

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

When I do this it replaces the special characters with "\\". But when I print the string, it prints with single slash. I thought it is taking single slash only but when I debugged I found that the variable is taking "\\".

当我这样做时，它将特殊字符替换为 "\\". 但是当我打印字符串时，它用单斜杠打印。我以为它只使用单斜杠，但是当我调试时，我发现该变量正在使用"\\".

Can anyone suggest how to replace the special characters with single slash ("\")?

谁能建议如何用单斜杠 ( "\")替换特殊字符？

回答by polygenelubricants

On escape sequences

关于转义序列

A declaration like:

像这样的声明：

String s = "\";

defines a string containing a single backslash. That is, s.length() == 1.

定义一个包含单个反斜杠的字符串。也就是说，s.length() == 1。

This is because \is a Java escape character for Stringand charliterals. Here are some other examples:

这是因为\是String和char文字的 Java 转义字符。以下是一些其他示例：

• "\n"is a Stringof length 1 containing the newline character
• "\t"is a Stringof length 1 containing the tab character
• "\""is a Stringof length 1 containing the double quote character
• "\/"contains an invalid escape sequence, and therefore is not a valid Stringliteral
  • it causes compilation error

• "\n"是String包含换行符的长度为 1 的
• "\t"是String包含制表符的长度为 1 的
• "\""是String包含双引号字符的长度为 1 的
• "\/"包含无效的转义序列，因此不是有效的String文字
  • 它导致编译错误

Naturally you can combine escape sequences with normal unescaped characters in a Stringliteral:

自然地，您可以在String文字中将转义序列与普通的未转义字符组合起来：

System.out.println("\"Hey\\nHow\tare you?");

The above prints (tab spacing may vary):

以上打印（标签间距可能会有所不同）：

"Hey\
How are you?

References

参考

• JLS 3.10.6 Escape Sequences for Character and String Literals

• JLS 3.10.6 字符和字符串文字的转义序列

See also

也可以看看

• Is the char literal '\"'the same as '"'?(backslash-doublequote vs only-doublequote)

• char 文字'\"'是否与'"'?（反斜杠双引号 vs 仅双引号）相同

---

---

Back to the problem

回到问题

Your problem definition is very vague, but the following snippet works as it should:

您的问题定义非常模糊，但以下代码段按其应有的方式工作：

System.out.println("How are you? Really??? Awesome!".replace("?", "\?"));

The above snippet replaces ?with \?, and thus prints:

上面的代码片段替换?为\?, 从而打印：

How are you\? Really\?\?\? Awesome!

If instead you want to replace a charwith another char, then there's also an overload for that:

相反，如果您想char用 another替换 a char，那么还有一个重载：

System.out.println("How are you? Really??? Awesome!".replace('?', '\'));

The above snippet replaces ?with \, and thus prints:

上面的代码片段替换?为\, 从而打印：

How are you\ Really\\ Awesome!

StringAPI links

String接口链接

• replace(CharSequence target, CharSequence replacement)
  • Replaces each substring of this string that matches the literal targetsequence with the specified literal replacementsequence.
• replace(char oldChar, char newChar)
  • Returns a new string resulting from replacing all occurrences of oldCharin this string with newChar.

• replace(CharSequence target, CharSequence replacement)
  • target用指定的文字replacement序列替换此字符串中与文字序列匹配的每个子字符串。
• replace(char oldChar, char newChar)
  • 返回一个新字符串oldChar，该字符串是用替换此字符串中所有出现的newChar。

---

---

On how regex complicates things

关于正则表达式如何使事情复杂化

If you're using replaceAllor any other regex-based methods, then things becomes somewhat more complicated. It can be greatly simplified if you understand some basic rules.

如果您正在使用replaceAll或任何其他基于正则表达式的方法，那么事情会变得有些复杂。如果您了解一些基本规则，则可以大大简化。

• Regex patterns in Java is given as Stringvalues
• Metacharacters (such as ?and .) have special meanings, and may need to be escaped by preceding with a backslash to be matched literally
• The backslash is also a special character in replacement Stringvalues

• Java 中的正则表达式模式以String值的形式给出
• 元字符（如?and .）有特殊含义，可能需要在前面加上反斜杠进行转义，才能按字面意思匹配
• 反斜杠也是替换String值中的特殊字符

The above factors can lead to the need for numerous backslashes in patterns and replacement strings in a Java source code.

上述因素可能导致在 Java 源代码中的模式和替换字符串中需要大量反斜杠。

It doesn't look like you need regex for this problem, but here's a simple example to show what it can do:

看起来你不需要正则表达式来解决这个问题，但这里有一个简单的例子来展示它可以做什么：

    System.out.println(
        "Who you gonna call? GHOSTBUSTERS!!!"
            .replaceAll("[?!]+", "<
Who you gonna call<?> GHOSTBUSTERS<!!!>
>")
    );

The above prints:

上面的打印：

str.replace("?", "\?")

str.replaceAll("\?","\\?");

The pattern [?!]+matches one-or-more (+) of any characters in the character class [...]definition (which contains a ?and !in this case). The replacement string <$0>essentially puts the entire match $0within angled brackets.

该模式[?!]+匹配+字符类[...]定义中的一个或多个 ( ) （在本例中包含 a?和!）。替换字符串<$0>基本上将整个匹配项$0放在尖括号内。

Related questions

相关问题

• Having trouble with Splitting text.- discusses common mistakes like split(".")and split("|")

• 拆分文本时遇到问题。- 讨论常见的错误，如split(".")和split("|")

Regular expressions references

正则表达式参考

• regular-expressions.info
  • Character classand Repetition with Star and Plus
• java.util.regex.Patternand Matcher

• 正则表达式.info
  • 使用 Star 和 Plus 进行字符类和重复
• java.util.regex.Pattern和 Matcher

回答by True Soft

In case you want to replace ?with \?, there are 2 possibilities: replaceand replaceAll(for regular expressions):

如果您想替换?为\?，有两种可能性：replace和replaceAll（对于正则表达式）：

        String str="\";
        str=str.replace(str,"\\");
        System.out.println("New String="+str);

The result is "The . startup trace \?state is info\?"

结果是 "The . startup trace \?state is info\?"

If you want to replace ?with \, just remove the ?character from the second argument.

如果要替换?为\，只需?从第二个参数中删除该字符。

回答by user207421

But when I print the string, it prints with single slash.

但是当我打印字符串时，它用单斜杠打印。

Good. That's exactly what you want, isn't it?

好的。这正是你想要的，不是吗？

There are two simple rules:

有两个简单的规则：

1. A backslash inside a String literal has to be specified as two to satisfy the compiler, i.e. "\". Otherwise it is taken as a special-character escape.

2. A backslash in a regular expresion has to be specified as two to satisfy regex, otherwise it is taken as a regexescape. Because of (1) this means you have to write 2x2=4 of them:"\\\\" (and because of the forum software I actually had to write 8!).

1. 字符串文字中的反斜杠必须指定为两个以满足编译器的要求，即“\”。否则，它被视为特殊字符转义。

2. 正则表达式中的反斜杠必须指定为两个以满足正则表达式，否则将被视为正则表达式转义。因为 (1) 这意味着你必须写 2x2=4 个："\\\\"（而且因为论坛软件，我实际上不得不写 8 个！）。

回答by JDGuide

##代码##

Out put:- New String=\

输出：- 新字符串=\

In java "\\"treat as "\". So, the above code replace a "\"single slash into "\\".

在 java 中"\\"视为"\". 因此，上面的代码将"\"单个斜杠替换为"\\".