Exercise: Person details display

Your task is to implement formatPersonDisplay function: It should have String result type and the following parameters:

• name of type String? and default value null.
• surname of type String? and default value null.
• age of type Int? and default value null.

Beware! Parameter types should include ?, so those should be String? and Int? instead of String and Int. This is because we want to allow passing null as a parameter value. This will be explained in the chapter Nullability.

Function should return a string in the following format: "{name} {surname} ({age})". If any of the parameters is null, it should be omitted from the result. If all parameters are null, it should return an empty string.

Here are some examples of how the function should work:

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)

This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in essentials/functions/PersonDisplay.kt. You can find there example usage and unit tests.

In this project, example usage and unit tests are commented not to prevent other files from compilation. To uncomment them, select commented lines and use command + / on Mac (Ctrl + / on Windows)

Hint: You can use trim function on a string to remove leading and trailing whitespace characters.

Once you are done with the exercise, you can check your solution here.

Playground

import org.junit.Test
import kotlin.test.assertEquals

// TODO

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))
    }
}