Int, Long, Float, Double number types in Kotlin - Mini Project: Build & Apply

Working with Int, Long, Float, and Double Number Types in Kotlin

📖 Scenario: You are creating a simple Kotlin program to store and display different types of numbers used in real life, such as counting items, measuring distances, or recording temperatures.

🎯 Goal: Build a Kotlin program that declares variables of type Int, Long, Float, and Double, assigns them specific values, and then prints these values.

📋 What You'll Learn

Create variables with exact names and values as instructed

Use Kotlin number types: Int, Long, Float, Double

Print the values exactly as shown

💡 Why This Matters

🌍 Real World

Number types like Int, Long, Float, and Double are used in apps to store counts, distances, prices, and measurements accurately.

💼 Career

Understanding these types helps you write programs that handle numbers correctly, which is essential for software development in finance, science, and many other fields.

1

Create Int and Long variables

Create a variable called countItems of type Int and set it to 150. Then create a variable called distanceInMeters of type Long and set it to 9876543210L.

Kotlin

# Create variables countItems and distanceInMeters with given values
# Your code here

Hint

Remember to add L at the end of the Long value.

2

Create Float and Double variables

Create a variable called temperatureFloat of type Float and set it to 36.6F. Then create a variable called temperatureDouble of type Double and set it to 36.65.

Kotlin

val countItems: Int = 150
val distanceInMeters: Long = 9876543210L
# Create variables temperatureFloat and temperatureDouble with given values
# Your code here

Hint

Remember to add F at the end of the Float value.

3

Use variables in expressions

Create a variable called totalTemperature of type Double that adds temperatureFloat and temperatureDouble. Use explicit conversion to Double for temperatureFloat.

Kotlin

val countItems: Int = 150
val distanceInMeters: Long = 9876543210L
val temperatureFloat: Float = 36.6F
val temperatureDouble: Double = 36.65
# Create totalTemperature by adding temperatureFloat and temperatureDouble
# Your code here

Hint

Use toDouble() to convert Float to Double before adding.

4

Print all variable values

Print the values of countItems, distanceInMeters, temperatureFloat, temperatureDouble, and totalTemperature each on a new line using println.

Kotlin

val countItems: Int = 150
val distanceInMeters: Long = 9876543210L
val temperatureFloat: Float = 36.6F
val temperatureDouble: Double = 36.65
val totalTemperature: Double = temperatureFloat.toDouble() + temperatureDouble
# Print all variable values below
# Your code here

Hint

Use println for each variable to print its value on a new line.

Practice

1. Which Kotlin number type should you use to store a whole number like 42?

easy

A. Float

B. Double

C. Int

D. Long

Solution

1. Step 1: Understand the number type categories

   Int is used for normal whole numbers without decimals.

2. Step 2: Match the number 42 to the type

   42 is a whole number and fits in Int range.

3. Final Answer:

   Int -> Option C

4. Quick Check:

   Whole number 42 = Int [OK]

Hint: Whole numbers without decimals use Int by default [OK]

Common Mistakes:

• Choosing Float or Double for whole numbers
• Using Long unnecessarily for small numbers

2. Which of the following is the correct way to declare a Float variable with value 3.14 in Kotlin?

easy

A. val pi: Float = 3.14

B. val pi: Float = 3.14Ff

C. val pi: Float = 3.14d

D. val pi: Float = 3.14f

Solution

1. Step 1: Recall Kotlin Float literal syntax

   Float literals require an 'f' or 'F' suffix to distinguish from Double.

2. Step 2: Check each option

   val pi: Float = 3.14f uses '3.14f' which is correct. val pi: Float = 3.14 misses the suffix. val pi: Float = 3.14Ff has invalid suffix 'Ff'. val pi: Float = 3.14d uses 'd' which is for Double.

3. Final Answer:

   val pi: Float = 3.14f -> Option D

4. Quick Check:

   Float literals end with 'f' [OK]

Hint: Add 'f' suffix to decimal for Float type [OK]

Common Mistakes:

• Omitting 'f' suffix for Float literals
• Using 'd' suffix which is for Double
• Using invalid suffixes like 'Ff'

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

val a: Int = 100000
val b: Long = 10000000000L
val c: Float = 3.14f
val d: Double = 3.1415926535
println("$a $b $c $d")

medium

A. 100000 10000000000 3.1400001 3.1415926535

B. 100000 10000000000 3.14 3.1415926535

C. 100000 10000000000 3.14f 3.1415926535

D. 100000 10000000000 3.14 3.1415927

Solution

1. Step 1: Understand variable types and precision

   a is Int (100000), b is Long (10000000000L), c is Float (3.14f), d is Double (3.1415926535).

2. Step 2: Check printed values and precision

   Float prints as 3.1400001 due to precision limits, Double prints full precision (3.1415926535). So output matches 100000 10000000000 3.1400001 3.1415926535.

3. Final Answer:

   100000 10000000000 3.1400001 3.1415926535 -> Option A

4. Quick Check:

   Float prints with slight precision difference [OK]

Hint: Float prints decimals with limited precision [OK]

Common Mistakes:

• Thinking Float prints exactly 3.14
• Confusing Float and Double precision
• Misreading Long large number formatting

4. Identify the error in this Kotlin code snippet:

val bigNumber: Long = 12345678901234567890
val smallNumber: Int = 2147483648

medium

A. Both numbers are too large for their types

B. Only bigNumber is too large for Long

C. No errors, code is correct

D. Only smallNumber is too large for Int

Solution

1. Step 1: Check Long value range

   Long can hold values up to 9,223,372,036,854,775,807. The bigNumber literal exceeds this, so it causes an error.

2. Step 2: Check Int value range

   Int max is 2,147,483,647. The smallNumber is 2,147,483,648 which is 1 more than max, so it causes an error.

3. Step 3: Analyze the code

   Both literals are too large for their types, causing compile errors.

4. Final Answer:

   Both numbers are too large for their types -> Option A

5. Quick Check:

   Int max 2147483647, Long max 9223372036854775807; both exceeded [OK]

Hint: Check max values: Int max 2,147,483,647; Long max 9,223,372,036,854,775,807 [OK]

Common Mistakes:

• Ignoring suffix 'L' for Long literals
• Assuming Long can hold any big number
• Not checking Int max value

5. You want to store the population of a country which is about 1.4 billion people. Which Kotlin type is best and why?

Options:
A) Long because it can store very large whole numbers
B) Int because it stores whole numbers
C) Float because it stores decimal numbers
D) Double because it stores decimal numbers with more precision

hard

A. Int because it stores whole numbers

B. Long because it can store very large whole numbers

C. Float because it stores decimal numbers

D. Double because it stores decimal numbers with more precision

Solution

1. Step 1: Understand the population size and type limits

   Population is about 1.4 billion (1,400,000,000). Int max is 2,147,483,647, so Int can hold it.

2. Step 2: Consider best practice for large numbers

   Though Int can hold 1.4 billion, Long is safer for very large whole numbers and future growth.

3. Step 3: Decide on the best type

   Long is best because it can store very large whole numbers beyond Int range.

4. Final Answer:

   Long because it can store very large whole numbers -> Option B

5. Quick Check:

   Long preferred for large integers like population [OK]

Hint: Use Long for very large whole numbers like population [OK]

Common Mistakes:

• Choosing Int without considering future growth
• Using Float or Double for whole numbers unnecessarily
• Ignoring future growth beyond Int range