Comparison operators in Kotlin - Mini Project: Build & Apply

Comparison Operators in Kotlin

📖 Scenario: You are helping a store manager compare product prices to decide which items are cheaper or more expensive.

🎯 Goal: Build a Kotlin program that compares two product prices using comparison operators and shows the results.

📋 What You'll Learn

Create two variables with exact prices

Create a variable to hold a threshold price

Use comparison operators to compare prices with the threshold

Print the comparison results clearly

💡 Why This Matters

🌍 Real World

Comparing prices helps shoppers and store managers decide which products are cheaper or more expensive.

💼 Career

Understanding comparison operators is essential for decision-making logic in software development.

1

Create product price variables

Create two variables called priceA and priceB with values 150 and 200 respectively.

Kotlin

# Create variables priceA and priceB with values 150 and 200
// Your code here

Hint

Use val to create variables and assign the exact numbers.

2

Add a threshold price variable

Create a variable called threshold and set it to 180.

Kotlin

val priceA = 150
val priceB = 200
// Create a variable threshold with value 180
// Your code here

Hint

Use val threshold = 180 to create the variable.

3

Compare prices with threshold

Create two Boolean variables called isPriceALess and isPriceBMore. Set isPriceALess to the result of priceA < threshold and isPriceBMore to the result of priceB > threshold.

Kotlin

val priceA = 150
val priceB = 200
val threshold = 180
// Create isPriceALess and isPriceBMore using comparison operators
// Your code here

Hint

Use < and > operators to compare values.

4

Print the comparison results

Print the values of isPriceALess and isPriceBMore using two separate println statements.

Kotlin

val priceA = 150
val priceB = 200
val threshold = 180
val isPriceALess = priceA  threshold
// Print isPriceALess and isPriceBMore
// Your code here

Hint

Use println(isPriceALess) and println(isPriceBMore) to show the results.

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