sortedByDescending (original) (raw)

Returns a list of all elements sorted descending according to natural sort order of the value returned by specified selector function.

The sort is stable. It means that elements for which selector returned equal values preserve their order relative to each other after sorting.

Since Kotlin

1.0

Samples

import kotlin.math.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   class Dish(val name: String, val calories: Int, val tasteRate: Float) {
    override fun toString(): String = "Dish($name: <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>a</mi><mi>l</mi><mi>o</mi><mi>r</mi><mi>i</mi><mi>e</mi><mi>s</mi><mi>c</mi><mi>a</mi><mi>l</mi><mo separator="true">,</mo><mi>t</mi><mi>a</mi><mi>s</mi><mi>t</mi><mi>e</mi></mrow><annotation encoding="application/x-tex">calories cal, taste </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">c</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal" style="margin-right:0.02778em;">or</span><span class="mord mathnormal">i</span><span class="mord mathnormal">esc</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">a</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span></span></span></span>tasteRate/5)"
}

val fridgeContent = listOf(Dish("🥦", 34, 2.3f), Dish("🧃", 34, 4.9f), Dish("🍨", 207, 4.7f))

val tastyDishes = fridgeContent.sortedByDescending { it.tasteRate }
println(tastyDishes) // [Dish(🧃: 34 cal, taste 4.9/5), Dish(🍨: 207 cal, taste 4.7/5), Dish(🥦: 34 cal, taste 2.3/5)]

val energeticDishes = fridgeContent.sortedByDescending { it.calories }
// note that the sorting is stable, so the 🥦 is before the 🧃
println(energeticDishes) // [Dish(🍨: 207 cal, taste 4.7/5), Dish(🥦: 34 cal, taste 2.3/5), Dish(🧃: 34 cal, taste 4.9/5)]

// the original collection remains unchanged
println(fridgeContent) // [Dish(🥦: 34 cal, taste 2.3/5), Dish(🧃: 34 cal, taste 4.9/5), Dish(🍨: 207 cal, taste 4.7/5)] 
   //sampleEnd
}

Returns a list of all elements sorted descending according to natural sort order of the value returned by specified selector function.

The sort is stable. It means that elements for which selector returned equal values preserve their order relative to each other after sorting.

Since Kotlin

1.0

Samples

import kotlin.math.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   val unsorted = intArrayOf(3, 1, 2, 4)

val sortedByValue = unsorted.sortedByDescending { it % 3 }
// the sorting is stable: the order of 1 (1 % 3 == 1) and 4 (4 % 3 == 1) was preserved
println(sortedByValue) // [2, 1, 4, 3]

val mapping = mapOf(1 to "one", 2 to "two", 3 to "three", 4 to "four")
val sortedByPronunciation = unsorted.sortedByDescending {
    // take a key to sort by from the mapping
    mapping.getOrDefault(it, "unknown")
}
// two > three > one > four, lexicographically
println(sortedByPronunciation) // [2, 3, 1, 4]

// the original array remains unchanged
println(unsorted.toList()) // [3, 1, 2, 4] 
   //sampleEnd
}