How to replace multiple slash and backslash in a string with a single one?

Question

My goal is to replace all "/" and "\" with one "\".

Input:

String path = "H\\\\\\\\\\ello///Wo\\rld\\!////";

Output:

String path = "H\ello\Wo\rld\!\";

Question:

Is there a way to do that all in one single line?

My solution (working!):

change all to the same char
replace all "/" with one Slash
put it back to normal

I learned that I need regex and that "[X]+" will put all possible combinations eg. "XXfXfXXXX" to "XfXfX".

I am searching for something like: (pseudocode)

path = path.replaceAll("[\\/]+", "\\");

I tried some combinations of that but everytime it throw errors.

My Solution:

path = path.replace("\\", "/");
path = path.replaceAll("[/]+", "/");

pfad = pfad.replace("/", "\\");

I'm afraid you'll have to iterate here thru the chars one by one — Naya
– Naya, Commented Apr 29, 2019 at 13:27
Why do you want to replace \ with \? It doesn't change anything. Do you perhaps want to replace series of \ and / with single \? — Pshemo
– Pshemo, Commented Apr 29, 2019 at 13:29
Try .replaceAll("[\\\\/]+", "\\\\") if all chunks of 1 or more \ and / chars should be replaced with one \. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Apr 29, 2019 at 13:30
What should be result of replacing \\\\//? Should it be one \ or maybe two \\ (one for \\\\ sequence and second for // sequence)? — Pshemo
– Pshemo, Commented Apr 29, 2019 at 13:35

Michał Turczyn · Accepted Answer · 2019-04-29 13:37:02Z

4

Try this pattern to match groups of slashes and backslashes: (?:\\+|\/+) and replace it with \\.

Explanation:

(?:...) - noncapturing group

\\+ - match one or more \

\/+ - match one or more /

| - alternation: match pattern on the right or on the left

Demo

Alternatively you could use pattern [\/\\]+, which matches one or more of \ or /

Another demo

edited Apr 29, 2019 at 13:37

answered Apr 29, 2019 at 13:30

Michał Turczyn

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10 Comments

SamWhan Over a year ago

This won't work if there's a mix of back- and forward-slashes. E.g. H\\\\///\\\ello///Wo\\rld\!/\//. It might be good enough for OP though ;)

Michał Turczyn Over a year ago

@SamWhan That's why I included alternative, which would work in your scenario :)

Strelok Over a year ago

Simply [\\\/]+ is sufficient

Michał Turczyn Over a year ago

@Strelok That's why I also suggested it

Wiktor Stribiżew Over a year ago

No need to escape / char, it is not any special in a regex.

|

Wiktor Stribiżew · Accepted Answer · 2019-04-29 14:50:11Z

3

Use

.replaceAll("[\\\\/]+", "\\\\")

See the regex graph:

The [\\/]+ pattern matches \ or / one or more times. The replacement pattern is \\ since a backslash in the replacement pattern is special in Java, it is used to escape the $ symbol that denotes a literal $ char. To match a literal backslash, you need to use four \ in the regex string literal.

See Java demo online:

String path = "H\\\\\\\\\\ello///Wo\\rld\\!////";
System.out.println(path.replaceAll("[\\\\/]+", "\\\\"));
// => H\ello\Wo\rld\!\

edited Apr 29, 2019 at 14:50

answered Apr 29, 2019 at 14:44

Wiktor Stribiżew

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