Why string handling matters in Kotlin - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the length of the string.

Kotlin

val text = "Hello, Kotlin!"
println(text.[1])

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

Asize

Blength()

Ccount

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() with parentheses causes an error because length is a property, not a function.

In Kotlin, length is a property of the String class that gives the number of characters.

2fill in blank

medium

Complete the code to convert the string to uppercase.

Kotlin

val greeting = "hello"
val shout = greeting.[1]()

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

Auppercase

BtoUpperCase

CtoLowerCase

DupperCase

Attempts:

3 left

💡 Hint

Common Mistakes

Using toUpperCase() which is deprecated in Kotlin 1.5+.

Using upperCase() which is not a valid function.

The correct function in Kotlin to convert a string to uppercase is uppercase().

3fill in blank

hard

Fix the error in the code to check if the string starts with "Hi".

Kotlin

val message = "Hi there!"
val starts = message.[1]("Hi")

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

AbeginWith

BstartsWith

Cstarts

DstartWith

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the function name causes a compilation error.

The correct function to check the start of a string is startsWith().

4fill in blank

hard

Fill both blanks to create a map of words to their lengths for words longer than 3 characters.

Kotlin

val words = listOf("apple", "bat", "car", "door")
val lengths = words.associateWith { it.[1] }.filter { it.value [2] 3 }

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

Alength

B>

C<

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > causes filtering of shorter words instead.

Using count() instead of length property causes an error.

Use length to get the word length and > to filter words longer than 3 characters.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths for words containing 'a'.

Kotlin

val words = listOf("apple", "bat", "car", "door")
val result = words.filter { it.[1]('a') }.associate { it.[2]() to it.[3] }

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

Acontains

Buppercase

Clength

DstartsWith

Attempts:

3 left

💡 Hint

Common Mistakes

Using startsWith instead of contains misses words with 'a' not at start.

Forgetting parentheses on uppercase() causes errors.

Use contains to check for 'a', uppercase() to convert words, and length for their lengths.

Practice

1. Why is string handling important in Kotlin programming?

easy

A. It controls the hardware devices directly.

B. It speeds up the computer's processor.

C. It helps us work with text like messages and user input.

D. It manages memory allocation automatically.

Solution

1. Step 1: Understand the role of strings in programs

   Strings represent text, which is essential for messages, input, and output.

2. Step 2: Identify why handling strings matters

   Handling strings allows programs to display messages and process user input effectively.

3. Final Answer:

   It helps us work with text like messages and user input. -> Option C

4. Quick Check:

   String handling = working with text [OK]

Hint: Strings = text handling in programs [OK]

Common Mistakes:

• Confusing string handling with hardware control
• Thinking string handling speeds up processors
• Mixing string handling with memory management

2. Which of the following is the correct way to create a string variable in Kotlin?

easy

A. val name = Kotlin

B. val name = "Kotlin"

C. var name := "Kotlin"

D. string name = 'Kotlin'

Solution

1. Step 1: Recall Kotlin string declaration syntax

   In Kotlin, strings are declared with val or var and use double quotes for text.

2. Step 2: Check each option

   val name = "Kotlin" uses val and double quotes correctly. Others have syntax errors or missing quotes.

3. Final Answer:

   val name = "Kotlin" -> Option B

4. Quick Check:

   String variable = val + "text" [OK]

Hint: Use val/var and double quotes for strings [OK]

Common Mistakes:

• Using single quotes for strings
• Missing quotes around text
• Using incorrect assignment operators

3. What will be the output of this Kotlin code?

val greeting = "Hello"
val name = "Anna"
println(greeting + ", " + name + "!")

medium

A. Hello, Anna!

B. Hello Anna!

C. Hello,Anna!

D. Hello Anna

Solution

1. Step 1: Understand string concatenation in Kotlin

   The + operator joins strings exactly as written, including commas and spaces.

2. Step 2: Combine the strings step-by-step

   "Hello" + ", " + "Anna" + "!" results in "Hello, Anna!" with comma and space.

3. Final Answer:

   Hello, Anna! -> Option A

4. Quick Check:

   Concatenate strings with + = Hello, Anna! [OK]

Hint: Check spaces and punctuation in concatenation [OK]

Common Mistakes:

• Ignoring spaces after commas
• Missing punctuation in output
• Confusing + with other operators

4. Find the error in this Kotlin code that tries to print a user's name:

val userName = 'John'
println("User: " + userName)

medium

A. Using single quotes instead of double quotes for string

B. Missing plus sign for concatenation

C. Incorrect variable name in println

D. No error, code is correct

Solution

1. Step 1: Check string declaration syntax

   Kotlin strings must use double quotes, not single quotes.

2. Step 2: Identify the error in userName assignment

   Using single quotes 'John' causes a syntax error; it should be "John".

3. Final Answer:

   Using single quotes instead of double quotes for string -> Option A

4. Quick Check:

   Strings need double quotes in Kotlin [OK]

Hint: Strings always use double quotes "" [OK]

Common Mistakes:

• Using single quotes for strings
• Assuming single quotes work like in other languages
• Ignoring syntax errors on string literals

5. You want to create a greeting message that includes a user's name and age in Kotlin. Which code correctly uses string templates to do this?

val name = "Sam"
val age = 25
val message = ???
println(message)

hard

A. val message = "Hello, $ name! You are $ age years old."

B. val message = 'Hello, $name! You are $age years old.'

C. val message = "Hello, " + name + "! You are " + age + " years old."

D. val message = "Hello, ${name}! You are ${age} years old."

Solution

1. Step 1: Understand Kotlin string templates

   Kotlin uses $variable or ${expression} inside double quotes to insert values.

2. Step 2: Compare options for correct template usage

   val message = "Hello, ${name}! You are ${age} years old." uses ${name} and ${age} correctly inside the string for clarity and safety.

3. Final Answer:

   val message = "Hello, ${name}! You are ${age} years old." -> Option D

4. Quick Check:

   Use ${} for variables in strings [OK]

Hint: Use ${} for variables inside strings [OK]

Common Mistakes:

• Using single quotes for strings
• Not using ${} for expressions
• Concatenating strings manually instead of templates