I have tried to fix this for a long time, and i just can't do it.
It could be any string, but this is an example:
"\This string \contains some\ backslashes\"
I need to make a regex that i can use to check that the string contains single backslashes.
I then need to convert the given string into (i can do the conversion):
"\\This string \\contains some\\ backslashes\\"
And then use regex to check that the string no long contains single backslashes.
Btw i dont have to use regex for this, i just need to be able to check the strings somehow.
It seems you just want to check if a string matches a regex pattern partially, namely, if it contains a literal backslash not preceded nor followed with a backslash.
Use
(?<!\\)\\(?!\\)
See the regex demo.
Sample Scala code:
val s = """"\This string\\ \contains some\ backslashes\""""
val rx = """(?<!\\)\\(?!\\)""".r.unanchored
val ismatch = s match {
case rx(_*) => true
case _ => false
}
println(ismatch)
See the Scala online demo.
Note:
"""(?<!\\)\\(?!\\)""".r.unanchored
- this line declares a regex object and makes the pattern unanchored, so that no full string match is no longer required by the match
block
- Inside
match
, we use case rx(_*)
as there is no capturing group defined inside the pattern itself
- The pattern means: match a backslash (
\\
) that is not preceded with a backslash ((?<!\\)
) and is not followed with a backslash ((?!\\)
).
Not sure what you're asking.. are you asking how to write a String literal that represents the String you gave as an example? You could either escape the backslash with another backslash, or use triple quotes.
scala> "\\This string \\contains some\\ backslashes\\"
String = \This string \contains some\ backslashes\
scala> """\This string \contains some\ backslashes\"""
String = \This string \contains some\ backslashes\
And replace the backslashes using the same techniques.
scala> "\\This string \\contains some\\ backslashes\\".replace("\\","\\\\")
String = \\This string \\contains some\\ backslashes\\
or
scala> """\This string \contains some\ backslashes\""".replace("""\""","""\\""")
String = \\This string \\contains some\\ backslashes\\
But I have a feeling you want to do something else, like validate input. Maybe you could provide a bit more context?
Try This
val s = """\This string \contains some\ backslashes\"""
s.replaceAll("""\\""","""\\\\""")