Replace characters from string using scala

Question

How to replace characters from a given string.

I wrote the following code, but here it iterates over the chars.

val chars = "\\`*{}[]()<>#+:~'%^&@?;,.\"!$=|"
var newString = inputString 
chars.map { c =>
  if (inputString.contains(c)){
    newString = newString.replace(c, '_')
  }
}

I'm looking at code similar to below. Unfortunately, it is throwing an error. Can someone help me to figure out the error?

scala> "hello:world".replaceAll("\\`*{}[]()>#+:~'%^&@<?;,\"!$=|.", "_")
java.util.regex.PatternSyntaxException: Illegal repetition near index 2
\`*{}[]()>#+:~'%^&@<?;,"!$=|.
^

It turns out that the first argument needs to be a regular expression for the argument, and not a list of characters, but I still get an error:

scala> "hello:world".replaceAll("[`*{}[]()>#+:~'%^&@<?;,\"!$=|.]", "_")
java.util.regex.PatternSyntaxException: Unclosed character class near index 29
[`*{}[]()>#+:~'%^&@<?;,"!$=|.]
                             ^

You have to escape the regex metacharacters correctly.

Matthias A. Eckhart
– Matthias A. Eckhart

2017-05-11 17:58:51 +00:00
Commented May 11, 2017 at 17:58 — Matthias A. Eckhart
– Matthias A. Eckhart, Commented May 11, 2017 at 17:58

GreyBeardedGeek · Accepted Answer · 2017-05-11 18:00:08Z

3

You did not escape all of the characters in the regex that need escaping. This works:

"hello:world".replaceAll("[\\`\\*{}\\[\\]()>#\\+:\\~'%\\^&@<\\?;,\"!\\$=\\|\\.]", "_")

but I'm guessing that what you really want is:

"hello:world".replaceAll("\\W", "_")

answered May 11, 2017 at 18:00

GreyBeardedGeek

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2 Comments

Cyrille Corpet Over a year ago

To avoid having to Java-escape the Regex-escape slash, you can also use triple double quotes. Besides, you forgot the slash, and the fact that some special characters need not be escaped in [] clause in regex: """[\`*{}\[]()>#+:~'%^&@<?;,"!$=|.]""".

ashawley Over a year ago

Yeah, the answer is correct. It just suffers from "backslash paranoia".

ashawley · Accepted Answer · 2017-05-11 18:14:47Z

2

If you escape the square braces with backslashes, the regular expression pattern should compile:

scala> "hello:world".replaceAll("[`*{}\\[\\]()>#+:~'%^&@<?;,\"!$=|.]", "_")
res0: String = hello_world

You could probably just use the character classes to write it more succinctly:

scala> "hello:world".replaceAll("\\p{Punct}", "_")
res1: String = hello_world

answered May 11, 2017 at 18:14

ashawley

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