How to replace 'n' back slashes (\) with one?

Question

I would like to squeeze out 'n' number of slashes into 1, where n is not fixed.

For example:

String path = "Report\\\\\\n";

Expected output : "Report\\n"

I tried the following way

System.out.println(path.replaceAll("\\+", "\");

But it's printing "Report\\\n"

I am not able to reduce more than that.

All the related so question/answer related to fixed number of slashes.

Is there any generic way I can squeeze all backslashes to one?

Check out [this posting](https://stackoverflow.com/questions/4025482/cant-escape-the-backslash-with-regex) for a good explanation of backslash escaping. — Markus L, Jul 27 '16 at 14:48
According to [documentation](https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#replaceAll(java.lang.String,%20java.lang.String) ) you should avoid replacing with single `backslash` using `String.replaceAll()`. It's recomended to use `Matcher`. — xenteros, Jul 27 '16 at 14:49

Maroun · Accepted Answer · 2016-07-27T15:08:13.730

5

If you print path, you'll get:

Report\\\n

That's because \ should be quoted and it's written as \\ in Java.

You should do:

System.out.println(path.replaceAll("\\\\+", "\\\\"));

Explanation:

In (pure) regex, in order to match the literal \, you should quote it. So it's represented as:

\\

In Java, \ is represented as \\, simple math should explain the 4 \s.

edited Jul 27 '16 at 15:08

answered Jul 27 '16 at 14:36

Maroun

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@Codebender Because `"\"` won't work as the compiler will think you quoted the `"`. You need to double-quote it. – Maroun Jul 27 '16 at 14:38
You are right. Looks the 2nd argument should be regex compatible too. Didn't know that. – Codebender Jul 27 '16 at 14:42
@MarounMaroun Could you please explain the logic? – nantitv Jul 27 '16 at 14:45
@nantitv in 30 mins I'll arrive home ans will explain my answer. – Maroun Jul 27 '16 at 14:50
@MarounMaroun I understood it. This have a nice explanation for it https://stackoverflow.com/questions/4025482/cant-escape-the-backslash-with-regex – nantitv Jul 27 '16 at 15:02
@nantitv It's indeed good explanation. I added mine to make the answer complete. Good luck. – Maroun Jul 27 '16 at 15:08

score 1 · Answer 2 · answered Jul 27 '16 at 14:38

1

You have to escape. A lot.

System.out.println("Report\\\\\\n");
System.out.println("Report\\\\\\n".replaceAll("[\\\\]+", "\\\\"));

Prints out:

Report\\\n
Report\n

answered Jul 27 '16 at 14:38

Murat Karagöz

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score 0 · Answer 3 · answered Jul 27 '16 at 14:37

0

You can use two method indexOf() and lastIndexOf() to get actual start and end index of string '\\....' Then simply get substring using substring method.

answered Jul 27 '16 at 14:37

Madgr

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score 0 · Answer 4 · edited Jul 27 '16 at 14:45

0

You just need the first and the last position of the "\" inside the String. Then create a String without the info between those positions.

int firstIndex = path.indexOf("\\");
int lastIndex = path.lastIndexOf("\\");
String result = path.substring(0, firstIndex) + path.substring(lastIndex, path.length());

edited Jul 27 '16 at 14:45

Klitos Kyriacou

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answered Jul 27 '16 at 14:40

dtenreiro

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Tenzin · Answer 5 · 2016-07-27T17:53:27.407

-1

For replacing multiple forward slashes with a single forward slash you could use:

.replaceAll("(?)[//]+", "/");

For replacing multiple backward slashes with a single backward slash you could use:

.replaceAll("(?)[\\\\]+", "\\\\");

edited Jul 27 '16 at 17:53

answered Jul 27 '16 at 14:35

Tenzin

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Why is my post -1, I tried my code out and it works. (Also i was one of the first to post... :-S) Can the one who downvoted my post at least give an explenation why it would be a negative answer. – Tenzin Jul 27 '16 at 17:57

How to replace 'n' back slashes (\) with one?

5 Answers5

Explanation: