Android string replacement using pattern

I am currently facing an issue in my android app when trying to search and replace a string.

I receive a sentence which contain the keyword ${keyword} it's coming like Today we are ${keyword} and it is beautiful I have to parse it and replace ${keyword} by a specific string

below is my code:

const val PATTERN_TO_FIND = "\${keyword}"

private val keywordRegex = Regex(ContentfulTranslations.PATTERN_TO_FIND)

fun replaceMyKeyword(sentence: String): String{
    return sentence.replace(keywordRegex, "blabla")
}

The app keeps crashing when parsing the sentence and looking for the pattern.

I already use this method and it used to work but the pattern to find wasn't formatted as ${keyword}

Any idea?

Thanks

The reason why it's crashing is that curly braces are reserved characters in regexp indicating a range, so you need to escape them (or at least the opening one). Moreover, \$ will put a literal $ sign at the beginning of your regexp, but dollar sign indicates the end of the string to match, so you need to "regexp-escape" it as well.. The end result would be:

const val PATTERN_TO_FIND = "\\\$\\{keyword}"

Luckily, Pattern class offers a utility method to automatically escape a regexp:

val pattern = Pattern.quote("\${keyword}")

Note that you still need to escape the dollar sign because it has a special meaning in Kotlin.

A full working example:

fun main() {
    val s = "Today we are \${keyword} and it is beautiful"

    val pattern = Pattern.quote("\${keyword}")
    val keywordRegex = Regex(pattern)

    println(s.replace(keywordRegex, "blabla"))
}

Will print:

Today we are blabla and it is beautiful