Char type and Unicode behavior in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Char variable holding the letter 'A'.

Kotlin

val letter: Char = '[1]'

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

A"A"

B'A'

CA

D'AA'

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes instead of single quotes for Char.

Trying to assign multiple characters to a Char.

In Kotlin, a Char is a single character enclosed in single quotes, like 'A'. Double quotes are for strings.

2fill in blank

medium

Complete the code to print the Unicode code of the Char 'Z'.

Kotlin

println([1].code)

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

A'Z'

B"Z"

C'z'

DZ

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes instead of single quotes.

Using a variable name without quotes.

The Char 'Z' is written with single quotes. The code property gives its Unicode number.

3fill in blank

hard

Fix the error in the code to convert an Int to a Char.

Kotlin

val ch: Char = 65.[1]()

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

AtoChar

BChar

CtoCharCode

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use Char() constructor with an Int.

Using a non-existent function like toCharCode.

In Kotlin, to convert an Int to a Char, use the toChar() function.

4fill in blank

hard

Fill both blanks to create a map of characters to their Unicode codes for letters 'a' to 'c'.

Kotlin

val map = mapOf([1] to [2], 'b' to 'b'.code, 'c' to 'c'.code)

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

A'a'

B'a'.code

C'b'

D'c'

Attempts:

3 left

💡 Hint

Common Mistakes

Using strings with double quotes instead of Chars.

Using Char without quotes.

The key is the Char 'a' and the value is its Unicode code using .code.

5fill in blank

hard

Fill all three blanks to create a list of Chars from Unicode codes 65 to 67.

Kotlin

val chars = listOf([1](65), 66.[2](), 67.[3]())

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

AChar

BtoChar

CtoChar()

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using toChar without parentheses.

Using lowercase 'char' which is invalid.

Use Char(65) to create a Char from code 65, or convert Int to Char with toChar(). Here, Char(65) and 66.toChar() are valid.

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