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Yahoo! JAPANとKotlin
This document contains code snippets demonstrating various Kotlin programming concepts including functions, null safety, extension functions, and asynchronous programming. It defines functions for squaring a number, sorting with a comparator, handling null values, extending the String class, and performing asynchronous operations with CompletableFuture to map and join results.
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Yahoo! JAPANとKotlin
- 5.
- 7. // val square:(Int) -> Int = { it * it } square(2) //-> 4 // fun sort(algorithm:(Int, Int) -> Boolean) { //... } sort { first, second -> first < second }
- 8.
- 9. //null var notNullable:String= "world" notNullable = null // //null var nullable:String? = "hello" nullable = null // if ? println(nullable?.capitalize())
- 11. fun String.twice() ="${this}, ${this}" println("hello".twice()) // -> hello, hello
- 19.
- 24. private fun startLongAsyncOperation(v:Int) = CompletableFuture.supplyAsync { Thread.sleep(1000) "Result: $v" } fun main(args: Array<String>) { val future = async<String> { (1..5).map { await(startLongAsyncOperation(it)) }.joinToString("n") } println(future.get()) } // 5 Result: 1 Result: 2 Result: 3 Result: 4 Result: 5