Why string handling matters in Kotlin - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code?

Consider the following Kotlin code that manipulates strings. What will it print?

Kotlin

fun main() {
    val text = "Kotlin"
    val result = text.substring(1, 4) + text.last()
    println(result)
}

A otln

B otlNn

C nNlto

D tlNn

💡 Hint

Remember substring(start, end) includes start but excludes end index.

The substring(1,4) extracts characters at indices 1, 2, and 3: 'o', 't', 'l'. The last character is 'n'. Concatenating gives 'otl' + 'n' = 'otln'.

🧠 Conceptual

intermediate

Why is string immutability important in Kotlin?

Which of the following best explains why strings in Kotlin are immutable?

A To allow strings to change their length dynamically.

B To allow multiple threads to safely share the same string without conflicts.

C To make strings faster to modify in place.

D To prevent strings from being garbage collected.

💡 Hint

Think about what happens when many parts of a program use the same string.

Immutable strings mean once created, they cannot change. This allows safe sharing across threads without unexpected changes or conflicts.

🔧 Debug

advanced

What error does this Kotlin code produce?

Examine the code below. What error will it cause when run?

Kotlin

fun main() {
    val s = "Hello"
    val c = s[5]
    println(c)
}

A SyntaxError

B NullPointerException

C No error, prints 'o'

D IndexOutOfBoundsException

💡 Hint

Remember string indices start at 0 and go up to length-1.

The string "Hello" has indices 0 to 4. Accessing s[5] is out of range, causing IndexOutOfBoundsException.

📝 Syntax

advanced

Which option correctly reverses a string in Kotlin?

Choose the Kotlin code snippet that correctly reverses the string "abcde".

A val reversed = "abcde".reversed()

B val reversed = "abcde".reverse()

C val reversed = "abcde".reversed

D val reversed = reverse("abcde")

💡 Hint

Check the exact function name and usage for reversing strings in Kotlin.

The correct function is reversed() with parentheses. reverse() does not exist for String, reversed is a function, not a property, and reverse() is not a top-level function.

🚀 Application

expert

How many items are in the resulting list?

What is the size of the list produced by splitting the string "one,two,,four," by comma in Kotlin?

Kotlin

fun main() {
    val input = "one,two,,four,"
    val parts = input.split(",")
    println(parts.size)
}

A 3

B 4

C 5

D 6

💡 Hint

Consider how split handles consecutive delimiters and trailing delimiters.

Splitting "one,two,,four," by comma produces: ["one", "two", "", "four", ""]. There are 5 items including empty strings for consecutive and trailing commas.