MISSION 1 OF 1

Curate a planet display

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Kotlin track: IntermediateMission: IntermediateCollection filteringLambda expressionsMapping

Before you start this intermediate track

Functions and collections. Read lambdas, nullable values, and conditional expressions.

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LEARN THE CONCEPT

Understand it, then try it.

A planetarium formats names for a small display. filter keeps the elements whose condition is true, while map transforms each retained element. Inside these single-parameter lambdas, it refers to the current name. joinToString combines the resulting list into readable text using the separator supplied by the display designer.

Main.kt

1fun main() {2    val planets = listOf("Saturn", "Earth", "Mars", "Venus")3    val display = planets.filter { it.length == 5 }4        .map { it.uppercase() }5    println(display.joinToString(" + "))6}

Each mission is a complete independent Kotlin/JVM program with its own main function. Run it with Kotlin 1.9 or later in a Kotlin playground or a configured Kotlin/JVM project. No Android APIs are required.

Track the values line by line. Predict the result before running this example in your own editor.

Read the official language documentation

kotlinlang.org/docs/collection-filtering.html kotlinlang.org/docs/null-safety.html kotlinlang.org/docs/control-flow.html