Why Kotlin over Java - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Kotlin variable with type inference.

Kotlin

val name = [1]

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A"John"

Bvar

CString

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' instead of a value

Using type name instead of value

Using 'val' again instead of a value

In Kotlin, you can declare a variable with val and assign a value directly. Here, the value should be a string literal like "John".

2fill in blank

medium

Complete the code to create a Kotlin function that returns the length of a string.

Kotlin

fun lengthOfString(str: String): Int = str.[1]

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Asize

Bcount

Clength()

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() with parentheses (Java style)

Using size which is for collections

Using count which requires a predicate

In Kotlin, strings have a length property (unlike Java's length() method) that returns the number of characters.

3fill in blank

hard

Fix the error in the Kotlin code to safely access the length of a nullable string.

Kotlin

val length = str[1]length ?: 0

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A?.

B?

C!!

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!!' which throws an exception if null

Using '?' alone which is incomplete

Using ':' which is for Elvis operator

The safe call operator ?. allows accessing properties of a nullable object without throwing an error if it's null.

4fill in blank

hard

Fill both blanks to create a Kotlin data class with two properties.

Kotlin

data class User(val name: [1], val age: [2])

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AString

BInt

CDouble

DBoolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using Double for age

Using Boolean for name

Mixing types incorrectly

A Kotlin data class holds data. Here, name is a String and age is an Int.

5fill in blank

hard

Fill all three blanks to create a Kotlin map comprehension filtering entries with values greater than 10.

Kotlin

val filtered = mapOf("a" to 5, "b" to 15, "c" to 20).filter { it.[1] [2] [3] }

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Avalue

B>

C10

Dkey

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'key' instead of 'value'

Using '<' instead of '>'

Using a wrong number

This code filters the map entries where the value is greater than 10.