Regular expressions with Regex class in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Regex object that matches the word "cat".

Kotlin

val pattern = Regex([1])
println(pattern.matches("cat"))

Drag options to blanks, or click blank then click option'

A"cat"

B"dog"

C"bat"

D"rat"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put the pattern inside quotes.

Using a wrong pattern string.

The Regex constructor takes a string pattern. To match "cat", we pass "cat" as the pattern.

2fill in blank

medium

Complete the code to check if the string "hello123" contains digits using Regex.

Kotlin

val regex = Regex([1])
println(regex.containsMatchIn("hello123"))

Drag options to blanks, or click blank then click option'

A"[a-z]+"

B"\\d+"

C"[A-Z]+"

D"\\w+"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a pattern that matches only letters.

Not escaping the backslash properly.

The pattern "\\d+" matches one or more digits. It detects digits in the string.

3fill in blank

hard

Fix the error in the code to find all words starting with 'a' in the text.

Kotlin

val text = "apple banana apricot avocado"
val regex = Regex([1])
val matches = regex.findAll(text).map { it.value }.toList()
println(matches)

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A"a+"

B"a*"

C"a\\w*"

D"a?"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "a*" which matches zero or more 'a's anywhere.

Using "a+" which requires at least one 'a' but not the following letters.

The pattern "a\\w*" matches words starting with 'a' followed by zero or more word characters.

4fill in blank

hard

Fill both blanks to create a Regex that matches email addresses and test it on a sample string.

Kotlin

val emailRegex = Regex([1])
val testEmail = "[e-mail]"
println(emailRegex.[2](testEmail))

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A"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}"

Bmatches

CcontainsMatchIn

Dfind

Attempts:

3 left

💡 Hint

Common Mistakes

Using containsMatchIn() which checks partial matches.

Using an incomplete regex pattern.

The regex pattern matches common email formats. Using matches() checks if the whole string matches the pattern.

5fill in blank

hard

Fill all three blanks to extract all numbers from a string and convert them to integers.

Kotlin

val input = "I have 2 apples and 10 bananas"
val numberRegex = Regex([1])
val numbers = numberRegex.findAll(input).map { it.[2].to[3]() }.toList()
println(numbers)

Drag options to blanks, or click blank then click option'

A"\\d+"

Bvalue

CInt

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'text' instead of 'value' to get the matched string.

Forgetting to convert the string to Int.

The pattern "\\d+" finds sequences of digits. Each match's value is converted to Int using toInt().