Solution: Person details display
This is the expected solution for this exercise:
fun formatPersonDisplay(
name: String? = null,
surname: String? = null,
age: Int? = null,
): String {
var result = ""
if (name != null) {
result += name
}
if (surname != null) {
result += " $surname"
}
if (age != null) {
result += " ($age)"
}
return result.trim()
}
This exercise can also be solved using functions that are presented in the Functional Kotlin book (the next book I recommend you reading after Kotlin Essentials). This is a solution using listOfNotNull and joinToString functions:
fun formatPersonDisplay(
name: String? = null,
surname: String? = null,
age: Int? = null,
): String = listOfNotNull(
name,
surname,
if (age != null) "($age)" else null
// or age?.let { "($it)" }
).joinToString(separator = " ")
This is a solution using buildString function (it allows constructing a string by appending it with next parts inside lambda expression block):
fun formatPersonDisplay(
name: String? = null,
surname: String? = null,
age: Int? = null,
): String = buildString {
if (name != null) append("$name")
if (surname != null) append(" $surname")
if (age != null) append(" ($age)")
}.trim()
Example solution in playground
import org.junit.Test
import kotlin.test.assertEquals
fun formatPersonDisplay(
name: String? = null,
surname: String? = null,
age: Int? = null,
): String {
var result = ""
if (name != null) {
result += name
}
if (surname != null) {
result += " $surname"
}
if (age != null) {
result += " ($age)"
}
return result.trim()
}
fun main() {
println(formatPersonDisplay("John", "Smith", 42))
// John Smith (42)
println(formatPersonDisplay("Alex", "Simonson"))
// Alex Simonson
println(formatPersonDisplay("Peter", age = 25))
// Peter (25)
println(formatPersonDisplay(surname="Johnson", age=18))
// Johnson (18)
}
class PersonDisplayTest {
@Test
fun testFormatPersonDisplay() {
val name = "John"
val surname = "Smith"
val age = 42
val expected = "John Smith (42)"
assertEquals(expected, formatPersonDisplay(name, surname, age))
}
@Test
fun testFormatPersonDisplayWithoutAge() {
val name = "Alex"
val surname = "Simonson"
val expected = "Alex Simonson"
assertEquals(expected, formatPersonDisplay(name, surname))
}
@Test
fun testFormatPersonDisplayWithoutSurname() {
val name = "Peter"
val age = 25
val expected = "Peter (25)"
assertEquals(expected, formatPersonDisplay(name = name, age = age))
}
@Test
fun testFormatPersonDisplayWithoutName() {
val surname = "Johnson"
val age = 18
val expected = "Johnson (18)"
assertEquals(expected, formatPersonDisplay(surname = surname, age = age))
}
@Test
fun testFormatPersonDisplayWithoutNameAndSurname() {
val age = 18
val expected = "(18)"
assertEquals(expected, formatPersonDisplay(age = age))
}
@Test
fun testFormatPersonDisplayWithoutParameters() {
val expected = ""
assertEquals(expected, formatPersonDisplay())
}
@Test
fun testFormatPersonDisplayWithNullName() {
val name: String? = null
val surname = "Smith"
val age = 42
val expected = "Smith (42)"
assertEquals(expected, formatPersonDisplay(name, surname, age))
}
@Test
fun testFormatPersonDisplayWithNullSurname() {
val name = "John"
val surname: String? = null
val age = 42
val expected = "John (42)"
assertEquals(expected, formatPersonDisplay(name, surname, age))
}
}
