CODEWITHSUNDEEP
jsonscala
Revathi P
Revathi P

Reputation: 97

Scala String Trim

I am trying to strip the string {"$outer":{}, (starts from curly brace and end with comma) in my input but I could not do it.

My input is like below

{"$outer":{},"size":"10","query":{"$outer":{},"match":{"$outer":{},"_all":{"$outer":{},"query":"VALLE","operator":"and"}}}}

I tried the below ways but both did not help me.

First Approach:

val dropString = "\"$outer\":{},"
val payLoadTrim = payLoadLif.dropWhile(_ == dropString).reverse.dropWhile(_ == dropString).reverse

This one did not do anything. Here is the output:

{"$outer":{},"size":"10","query":{"$outer":{},"match":{"$outer":{},"_all":{"$outer":{},"query":"VALLE","operator":"and"}}}}

Second Approach:

def stripAll(s: String, bad: String): String = {
@scala.annotation.tailrec def start(n: Int): String = 
    if (n == s.length) ""
    else if (bad.indexOf(s.charAt(n)) < 0) end(n, s.length)
    else start(1 + n)

@scala.annotation.tailrec def end(a: Int, n: Int): String =
    if (n <= a) s.substring(a, n)
    else if (bad.indexOf(s.charAt(n - 1)) < 0) s.substring(a, n)
    else end(a, n - 1)

  start(0)
}

Output from Second: 

size":"10","query":{"$outer":{},"match":{"$outer":{},"_all":{"$outer":{},"query":"VALLE","operator":"

and Desired Output:

{"size":"10","query":{"match":{"_all":{"query":"VALLE","operator":"and"}}}

Upvotes: 1

Views: 1106

Answers (2)

laughedelic
laughedelic

Reputation: 6460

When you need to cut off an exact prefix/suffix you can use .stripPrefix/.stripSuffix methods:

@ "abcdef".stripPrefix("abc")
res: String = "def"
@ "abcdef".stripSuffix("def")
res: String = "abc"

Note that if the string doesn't have such prefix (or suffix), it will stay unchanged: 

@ "abcdef".stripPrefix("foo")
res: String = "abcdef"
@ "abcdef".stripSuffix("buh")
res: String = "abcdef"

Sometimes it's important to cut off from the beginning (or end), so if when you use .replace, you should be careful and add ^... (or ...$) to the regex pattern, otherwise it may find a match somewhere in the middle and replace it.

Bonus: if you just want to check that a string has a given prefix/suffix, you can use .startsWith/.endsWith methods (plus .startsWith can also take an offset).

Upvotes: 0

Xavier Guihot
Xavier Guihot

Reputation: 61666

You might want to use replace:

val input = """{"$outer":{},"size":"10","query":{"$outer":{},"match":{"$outer":{},"_all":{"$outer":{},"query":"VALLE","operator":"and"}}}}"""

input.replace("\"$outer\":{},", "")

which returns:

{"size":"10","query":{"match":{"_all":{"query":"VALLE","operator":"and"}}}}

Upvotes: 3

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