Kotlin String - findAll() Function

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The Kotlin string findAll() function belongs to the regex class. It is used to find all matches of a regular expression in a char sequence or string.

This function is not a direct function of the Kotlin string class. But it is invoked via a regex object.

Use Cases of FindAll()

There are the following use cases of this function −

• It finds repeated pattern of substring in a string.
• It can parse structured data, such as CSV fields, URLs, or phone numbers.
• It extract all occurrences of a pattern in a string.

Syntax

Following is the syntax of the Kotlin string findAll() function −

fun Regex.findAll(input: CharSequence, startIndex: Int = 0): MatchResult?

Parameters

This function accepts following parameters −

• CharSequence: The string or charSequence in which we search for a match.
• startIndex: It is an optional parameter that represents an index from which we start searching in a string. The default is 0.

Return value

This function returns a sequence match result.

Example 1: Extracting All Digit

Following is the basic example of findAll() function: extracting all digit from a string −

fun main() {
   val regex = Regex("\\d+")
   val string = "tut12oria234lspo67int"
   val matches = regex.findAll(string)
   
   println("Display all digits: ")
   
   for (match in matches) {
      print(match.value + " ")
   }
}

Output

Following is the output −

Display all digits: 
12 234 67

Example 2: Extracting All Words

Let's see another example of the findAll() function: extracting all words starting from a specific letter from a string −

fun main() {
   // Matches words starting with 't'
   val regex = Regex("\\bt\\w*")
   val string = "tutorialspoint is a good edtech for tutorial. Keep Studying!"
   val matches = regex.findAll(string)

   for (match in matches) {
      println(match.value)
   }
}

Output

Following is the output −

tutorialspoint
tutorial

Example 3: Pattern Details

This example uses the findAll() function and accesses the details of each pattern match −

fun main() {
   // Matches one or more digits
   val regex = Regex("\\d+") 
   val string = "Order 123: price is 456 and tax is 789."
   val matches = regex.findAll(string)

   for (match in matches) {
      println("Matched value: ${match.value}")
      println("Start index: ${match.range.first}")
      println("End index: ${match.range.last}")
      println("---")
   }
}

Output

Following is the output −

Matched value: 123
Start index: 6
End index: 8
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Matched value: 456
Start index: 20
End index: 22
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Matched value: 789
Start index: 35
End index: 37
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