Comparison operators in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a is equal to b.

Kotlin

val result = (a [1] b)
println(result)

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

A=

B==

C!=

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using single = which is assignment, not comparison.

In Kotlin, == checks if two values are equal.

2fill in blank

medium

Complete the code to check if x is greater than y.

Kotlin

if (x [1] y) {
    println("x is greater")
}

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

A>

B>=

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of >.

The > operator checks if the left value is greater than the right value.

3fill in blank

hard

Fix the error in the code to check if num is not equal to 10.

Kotlin

val check = (num [1] 10)
println(check)

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

A=

B==

C!=

D<>

Attempts:

3 left

💡 Hint

Common Mistakes

Using = which is assignment, or <> which is not valid in Kotlin.

The != operator checks if two values are not equal in Kotlin.

4fill in blank

hard

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

Kotlin

val lengths = words.filter { word -> word.length > 3 }.associate { word -> [1] to [2] }

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

Aword

Bword.length

Cword.size

Dword.count()

Attempts:

3 left

💡 Hint

Common Mistakes

Using word.size or word.count() which are not properties of String in Kotlin.

The key should be the word itself, and the value should be its length using word.length.

5fill in blank

hard

Fill all three blanks to filter a map to only include entries where the value is greater than 5.

Kotlin

val filtered = map.filter { ([1], [2]) -> [2] [3] 5 }

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

Akey

Bvalue

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of >, or mixing up key and value.

In the lambda, key and value represent the map entry. We check if value > 5.

Practice

1. Which of the following Kotlin comparison operators checks if two values are equal?

easy

A. <=

B. !=

C. >

D. ==

Solution

1. Step 1: Understand the meaning of comparison operators

   In Kotlin, the operator == is used to check if two values are equal.

2. Step 2: Identify the correct operator for equality

   The operator == returns true if both values are equal, otherwise false.

3. Final Answer:

   == -> Option D

4. Quick Check:

   Equality operator = == [OK]

Hint: Remember: '==' means equal, '!=' means not equal [OK]

Common Mistakes:

• Confusing '==' with '=' which is assignment
• Using '!=' to check equality
• Mixing up '>' and '<=' operators

2. Which of the following is the correct Kotlin syntax to check if variable a is not equal to variable b?

easy

A. a != b

B. a <> b

C. a =! b

D. a !== b

Solution

1. Step 1: Recall Kotlin syntax for inequality

   Kotlin uses != to check if two values are not equal.

2. Step 2: Verify each option

   a != b is correct; a <> b is invalid in Kotlin; a =! b is incorrect syntax; a !== b checks referential inequality, not value inequality.

3. Final Answer:

   a != b -> Option A

4. Quick Check:

   Not equal operator = != [OK]

Hint: Use '!=' for not equal, never '<>' in Kotlin [OK]

Common Mistakes:

• Using '<>' which is not valid in Kotlin
• Swapping '=' and '!' in 'a =! b'
• Confusing '!=' with '!==', which checks references

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

val x = 10
val y = 20
println(x > y)

medium

A. false

B. true

C. 10

D. Compilation error

Solution

1. Step 1: Evaluate the comparison expression

   The expression x > y compares if 10 is greater than 20, which is false.

2. Step 2: Understand the println output

   Printing the boolean result of the comparison will output false.

3. Final Answer:

   false -> Option A

4. Quick Check:

   10 > 20 = false [OK]

Hint: Compare values carefully; 10 is not greater than 20 [OK]

Common Mistakes:

• Assuming 10 > 20 is true
• Confusing output with variable values
• Expecting a number instead of boolean output

4. Identify the error in this Kotlin code snippet:

val a = 5
val b = 10
if (a = b) {
    println("Equal")
} else {
    println("Not Equal")
}

medium

A. Variables a and b must be mutable

B. Missing semicolon after println

C. Using '=' instead of '==' in if condition

D. Incorrect println syntax

Solution

1. Step 1: Check the if condition syntax

   The condition uses a = b, which is assignment, not comparison.

2. Step 2: Correct the operator for comparison

   Use == to compare values, so it should be a == b.

3. Final Answer:

   Using '=' instead of '==' in if condition -> Option C

4. Quick Check:

   Comparison needs '==' not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Using '=' in if condition instead of '=='
• Thinking semicolons are required in Kotlin
• Assuming val variables must be mutable for comparison

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

val a = 7
val b = 7
val c = 10
println((a == b) && (b < c))

hard

A. false

B. true

C. 7

D. Compilation error

Solution

1. Step 1: Evaluate the first comparison (a == b)

   Since both a and b are 7, a == b is true.

2. Step 2: Evaluate the second comparison (b < c)

   Since 7 is less than 10, b < c is true.

3. Step 3: Evaluate the logical AND

   Both conditions are true, so true && true is true.

4. Final Answer:

   true -> Option B

5. Quick Check:

   (7 == 7) && (7 < 10) = true [OK]

Hint: Both conditions must be true for && to return true [OK]

Common Mistakes:

• Confusing && with || operator
• Misreading comparison results
• Expecting numeric output instead of boolean