String methods (substring, split, trim) in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of substring and trim

What is the output of this Kotlin code?

Kotlin

val text = "  Kotlin Programming  "
val result = text.trim().substring(0, 6)
println(result)

A " Kot"

B " Kotlin"

C "Kotlin "

D "Kotlin"

💡 Hint

Remember trim() removes spaces at the start and end before substring is applied.

The trim() removes spaces at both ends, so the string becomes "Kotlin Programming". Then substring(0,6) takes characters from index 0 up to 6 (not including 6), which is "Kotlin".

❓ Predict Output

intermediate

Splitting a string and accessing elements

What will be printed by this Kotlin code?

Kotlin

val data = "apple,banana, cherry, date"
val fruits = data.split(",")
println(fruits[2].trim())

A "banana"

B " cherry"

C "cherry"

D "date"

💡 Hint

Check how split works and remember to trim spaces after splitting.

Splitting by comma creates a list: ["apple", "banana", " cherry", " date"]. The element at index 2 is " cherry" with a space. After trim(), it becomes "cherry".

🔧 Debug

advanced

Identify the error in substring usage

What error will this Kotlin code produce?

Kotlin

val s = "Hello"
val sub = s.substring(3, 2)
println(sub)

A StringIndexOutOfBoundsException

B Prints "lo"

C Compilation error: wrong substring parameters

D No output, prints empty string

💡 Hint

Check the order of start and end indices in substring.

substring(startIndex, endIndex) requires startIndex <= endIndex. Here startIndex=3 and endIndex=2, which is invalid and throws StringIndexOutOfBoundsException.

❓ Predict Output

advanced

Count words after splitting and trimming

What is the output of this Kotlin code?

Kotlin

val sentence = "  Kotlin is fun  "
val words = sentence.trim().split(" ").filter { it.isNotEmpty() }
println(words.size)

A 2

B 3

C 5

D 4

💡 Hint

Trim removes spaces at ends, split by space, then filter removes empty strings.

After trim(), string is "Kotlin is fun". Splitting by space gives ["Kotlin", "is", "fun"]. None are empty, so size is 3.

🧠 Conceptual

expert

Understanding substring and split behavior

Given the Kotlin code below, what will be the output?

Kotlin

val input = "one,two,,four,"
val parts = input.split(",")
val sub = parts[2].substring(0, 0)
println("${parts.size} ${sub.isEmpty()}")

A "5 true"

B "4 false"

C "5 false"

D "4 true"

💡 Hint

Check how split handles consecutive commas and trailing commas, and substring with same start and end index.

Splitting "one,two,,four," by comma results in ["one", "two", "", "four", ""], so size is 5. substring(0,0) returns empty string, so isEmpty() is true.