Char type and Unicode behavior in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code with Char arithmetic?

Consider the following Kotlin code snippet. What will it print?

Kotlin

fun main() {
    val c: Char = 'A'
    val result = c + 2
    println(result)
}

A 67

B C

C Error: Operator '+' cannot be applied to 'Char' and 'Int'

D B

💡 Hint

Remember that Char plus Int results in an Int in Kotlin.

In Kotlin, adding an Int to a Char results in an Int representing the Unicode code point sum. 'A' has code 65, plus 2 is 67.

❓ Predict Output

intermediate

What does this Kotlin code print when converting Char to Int?

What is the output of this Kotlin program?

Kotlin

fun main() {
    val ch: Char = '\u03A9' // Greek capital letter Omega
    println(ch.code)
}

A 937

B Omega

C Error: 'code' property not found

D 0x03A9

💡 Hint

The 'code' property returns the Unicode code point as an Int.

The Unicode code point for Greek capital letter Omega (Ω) is 937 decimal.

❓ Predict Output

advanced

What is the output of this Kotlin code using Char ranges and contains?

Analyze the code and select the correct output.

Kotlin

fun main() {
    val vowels = 'a'..'u'
    println('e' in vowels)
    println('z' in vowels)
}

A

false
false

B

false
true

C

true
true

D

true
false

💡 Hint

Check if 'e' and 'z' fall within the range from 'a' to 'u'.

The range 'a'..'u' includes letters from 'a' to 'u'. 'e' is inside, 'z' is outside.

❓ Predict Output

advanced

What error does this Kotlin code raise when converting a Char to Int incorrectly?

What error will this code produce?

Kotlin

fun main() {
    val ch: Char = '1'
    val num: Int = ch
    println(num)
}

A Prints 1

B Prints 49

C Type mismatch: inferred type is Char but Int was expected

D No output, infinite loop

💡 Hint

Kotlin does not allow implicit conversion from Char to Int.

You cannot assign a Char directly to an Int variable without explicit conversion.

🧠 Conceptual

expert

How many characters are in this Kotlin string containing Unicode surrogate pairs?

Consider this Kotlin code snippet. How many characters does the string contain?

Kotlin

fun main() {
    val s = "\uD83D\uDE00" // Unicode emoji 😀 represented as surrogate pair
    println(s.length)
}

A 1

B 2

C 0

D Error at runtime

💡 Hint

Kotlin strings use UTF-16 encoding; surrogate pairs count as two chars.

The emoji 😀 is represented by two UTF-16 code units (surrogate pair), so length is 2.

Practice

1. Which of the following correctly declares a Char variable in Kotlin?

easy

A. val letter: Char = `A`

B. val letter: Char = "A"

C. val letter: Char = A

D. val letter: Char = 'A'

Solution

1. Step 1: Understand Char declaration syntax

   In Kotlin, a Char value must be enclosed in single quotes, like 'A'.

2. Step 2: Check each option

   val letter: Char = 'A' uses single quotes correctly. val letter: Char = "A" uses double quotes (String). val letter: Char = A has no quotes (invalid). val letter: Char = `A` uses backticks (invalid for Char).

3. Final Answer:

   val letter: Char = 'A' -> Option D

4. Quick Check:

   Char uses single quotes = A [OK]

Hint: Char values use single quotes, not double quotes [OK]

Common Mistakes:

• Using double quotes instead of single quotes
• Omitting quotes around the character
• Using backticks instead of quotes

2. Which of the following is the correct way to get the Unicode code of a Char in Kotlin?

easy

A. val code = 'A'.code

B. val code = 'A'.unicodeValue()

C. val code = 'A'.toInt()

D. val code = 'A'.unicode

Solution

1. Step 1: Recall Kotlin Char Unicode property

   Kotlin provides the code property to get the Unicode integer value of a Char.

2. Step 2: Evaluate options

   val code = 'A'.code uses code property correctly. val code = 'A'.toInt() uses toInt() which does not exist for Char. Options B and D use non-existent methods/properties.

3. Final Answer:

   val code = 'A'.code -> Option A

4. Quick Check:

   Use .code to get Unicode number [OK]

Hint: Use .code property to get Unicode number from Char [OK]

Common Mistakes:

• Using non-existent toInt() method on Char
• Trying non-existent methods like unicodeValue()
• Accessing properties that don't exist

3. What is the output of the following Kotlin code?

val ch: Char = 'Z'
println(ch.code)

medium

A. 122

B. 90

C. Z

D. SyntaxError

Solution

1. Step 1: Identify the Char and property used

   The variable ch is assigned the character 'Z'. The code prints ch.code, which returns the Unicode integer value.

2. Step 2: Find Unicode value of 'Z'

   The Unicode code for uppercase 'Z' is 90.

3. Final Answer:

   90 -> Option B

4. Quick Check:

   'Z'.code = 90 [OK]

Hint: Remember uppercase 'Z' Unicode is 90 [OK]

Common Mistakes:

• Confusing uppercase and lowercase Unicode values
• Expecting the character itself instead of code
• Thinking code property causes syntax error

4. Identify the error in this Kotlin code snippet:

val ch: Char = "A"
println(ch.code)

medium

A. code property does not exist for Char

B. Missing semicolon after println

C. Using double quotes for Char assignment

D. Variable ch should be Int, not Char

Solution

1. Step 1: Check Char assignment syntax

   Chars must be assigned using single quotes, not double quotes. Double quotes create a String.

2. Step 2: Verify other parts

   Semicolons are optional in Kotlin, so no error there. The code property exists for Char. Variable type Char is correct.

3. Final Answer:

   Using double quotes for Char assignment -> Option C

4. Quick Check:

   Char needs single quotes, not double [OK]

Hint: Chars use single quotes; double quotes mean String [OK]

Common Mistakes:

• Thinking semicolons are mandatory
• Believing code property is invalid
• Confusing Char and Int types

5. Given a list of characters val chars = listOf('a', 'B', 'c', 'D'), which Kotlin expression correctly filters only uppercase letters using Unicode properties?

hard

A. chars.filter { it.isUpperCase() }

B. chars.filter { it.code > 90 }

C. chars.filter { it.code.isUpperCase() }

D. chars.filter { it > 'Z' }

Solution

1. Step 1: Understand filtering uppercase letters

   Kotlin's Char class has a method isUpperCase() that returns true if the character is uppercase.

2. Step 2: Evaluate each option

   chars.filter { it.isUpperCase() } uses isUpperCase() correctly. chars.filter { it.code > 90 } filters by code > 90, which excludes all uppercase letters (A-Z: 65-90). chars.filter { it.code.isUpperCase() } calls isUpperCase() on an Int (code), which does not exist. chars.filter { it > 'Z' } compares chars incorrectly.

3. Final Answer:

   chars.filter { it.isUpperCase() } -> Option A

4. Quick Check:

   Use isUpperCase() to filter uppercase chars [OK]

Hint: Use isUpperCase() method to filter uppercase chars [OK]

Common Mistakes:

• Filtering by numeric code incorrectly
• Calling isUpperCase() on the Unicode code (Int)
• Using wrong comparison operators for chars