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Editorial Team
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Asked: 2026-06-10T07:51:40+00:00

How do I replace with \. Here is what im trying : def main(args:Array[String])

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How do I replace ” with \”.

Here is what im trying : 

def main(args:Array[String]) = {      
  val line:String = "replace \" quote";
  println(line);
  val updatedLine = line.replaceAll("\"" , "\\\"");
  println(updatedLine);
}

output : 

replace " quote
replace " quote

The output should be : 

replace " quote
replace \" quote
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1 Answer

  1. Editorial Team

    Two more \\ does the job: 

    scala>  line.replaceAll("\"" , "\\\\\"");
res5: java.lang.String = replace \" quote

    The problem here is that there are two ‘layers’ escaping the strings. The first layer is the compiler, which we can easily see in the REPL:

    scala> "\""
res0: java.lang.String = "

scala> "\\"
res1: java.lang.String = \

scala> "\\\""
res2: java.lang.String = \"

scala> val line:String = "replace \" quote";
line: String = replace " quote

    The second layer is the regular expression interpreter. This one is harder to see, but can be seen by applyin your example:

    scala>  line.replaceAll("\"" , "\\\"");
res5: java.lang.String = replace " quote

    What the reg. exp. interpreter really receives is \”, which is interpreted as only “. So, we need the reg. exp. to receive \\”. To make the compiler give us \ we need to write \\.

    Let’s see the unescaping:

    • The right case: \\\” the compiler sees \”, the regular expression sees \”.
    • The wrong case: \\” the compiler sees \”, the regular expression sees “.

    It can be a bit confusing despite being very straight forward.

    As pointed by @sschaef, another alternative it to use “”” triple-quoting, strings in this form aren’t unescaped by the compiler:

    scala>  line.replaceAll("\"" , """\\"""");
res6: java.lang.String = replace \" quote
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