Kotlin_Sequences

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Cases and Outputs

Case-1: sumByDouble()

fun exampleSumByDouble() {
    println("\nFind the total money gained from FOOD products")
    println("Iterable implementation")
    measure {
        val foodProducts = orders
            .flatMap { it.products }
            .filter { it.category == ProductCategory.FOOD }

        println("Total money gained from FOOD: ${foodProducts.sumByDouble { it.price }}")
    }

    println("Sequence implementation")
    measure {
        val foodProducts = orders
            .asSequence()
            .flatMap { it.products }
            .filter { it.category == ProductCategory.FOOD }

        println("Total money gained from FOOD: ${foodProducts.sumByDouble { it.price }}")
    }
}

Find the total money gained from FOOD products
Iterable implementation
Total money gained from FOOD: 3169452.9117080076
Time: 2824 ms
Sequence implementation
Total money gained from FOOD: 3169452.9117080076
Time: 681 ms

Case-2: average()

fun exampleAverage() {
    println("\nFind the average price of sold ELECTRONIC products")
    println("Iterable implementation")
    measure {
        val electronicProducts = orders
            .flatMap { it.products }
            .filter { it.category == ProductCategory.ELECTRONIC }
            .map { it.price }

        println("Average price of sold ELECTRONIC products: ${electronicProducts.average()}")
    }

    println("Sequence implementation")
    measure {
        val electronicProducts = orders
            .asSequence()
            .flatMap { it.products }
            .filter { it.category == ProductCategory.ELECTRONIC }
            .map { it.price }

        println("Average price of sold ELECTRONIC products: ${electronicProducts.average()}")
    }
}

Find the average price of sold ELECTRONIC products
Iterable implementation
Average price of sold ELECTRONIC products: 0.5017174426583605
Time: 933 ms
Sequence implementation
Average price of sold ELECTRONIC products: 0.5017174426583605
Time: 714 ms

Case-3: take()

fun exampleTake() {
    println("\nGet 100 CLOTHING products that price is bigger than 0.7")
    println("Iterable implementation")
    measure {
        val clothingProducts = orders
            .flatMap { it.products }
            .filter { it.category == ProductCategory.CLOTHING && it.price > 0.7 }
            .take(100)

        println("100 CLOTHING products that price is bigger than 0.7: $clothingProducts")
    }

    println("Sequence implementation")
    measure {
        val clothingProducts = orders
            .asSequence()
            .flatMap { it.products }
            .filter { it.category == ProductCategory.CLOTHING && it.price > 0.7 }
            .take(100)
            .toList()

        println("100 CLOTHING products that price is bigger than 0.7: $clothingProducts")
    }
}

Get 100 CLOTHING products that price is bigger than 0.7
Iterable implementation
100 CLOTHING products that price is bigger than 0.7: [Product(id=87995, name=e0d79a81-59c5-4988-989b-9b9ef4fab145, price=0.9912938603842654, category=CLOTHING), ...
Time: 550 ms
Sequence implementation
100 CLOTHING products that price is bigger than 0.7: [Product(id=87995, name=e0d79a81-59c5-4988-989b-9b9ef4fab145, price=0.9912938603842654, category=CLOTHING), ...
Time: 2 ms

Case-4: flatMap()

I got OutOfMemory exception when I tried with toList(). If you want to test with toList() you may decrease the ORDER_COUNT value.

fun exampleFlatMap(){
    println("\nTesting flatMap()")
    println("Iterable implementation")
    measure {
        val products = orders
            .flatMap { it.products }
            .toSet()
    }

    println("Sequence implementation")
    measure {
        val products = orders
            .asSequence()
            .flatMap { it.products }
            .toSet()
    }
}

Testing flatMap()
Iterable implementation
Time: 3326 ms
Sequence implementation
Time: 2238 ms