Kotlin：如何通过将字符重复给定次数来创建字符串

Question

我正在尝试在标题下方打印一行。这个想法是该行与标题的长度相同。我尝试了几种方法，我认为这是最接近的，但它给我的结果不正确。

fun main() {

    val chapters = arrayOf("Basic syntax", "Idioms", "Kotlin by example", "Coding conventions")

    for (numCharpter in chapters.indices){
        // Print the name of the chapter
        val title = "Charpter ${numCharpter + 1}: ${chapters[numCharpter]}"
        val arrayDash = Array(title.length) {'='}
        val stringDash = arrayDash.toString()


        println("$title\n$stringDash\n")

        // the rest of the code
    }
}

我想要的输出是：

Charpter 1: Basic syntax
========================

Charpter 2: Idioms
==================

Charpter 3: Kotlin by example
=============================

Charpter 4: Coding conventions
==============================

我得到的输出是：

Charpter 1: Basic syntax
[Ljava.lang.Character;@24d46ca6
Charpter 2: Idioms
[Ljava.lang.Character;@4517d9a3
Charpter 3: Kotlin by example
[Ljava.lang.Character;@372f7a8d
Charpter 4: Coding conventions
[Ljava.lang.Character;@2f92e0f4

有没有简单的方法通过重复一个字符来初始化字符串？

Answer 1

val chapters = arrayOf("Basic syntax", "Idioms", "Kotlin by example", "Coding conventions")

for (numCharpter in chapters.indices) {
  val title = "Chapter ${numCharpter + 1}: ${chapters[numCharpter]}"
  val line = "=".repeat(title.length)
  println("$title\n$line\n")
}

Answer 2

val chapters = arrayOf("Basic syntax", "Idioms", "Kotlin by example", "Coding conventions")

val titles = chapters.mapIndexed { index, chapter ->
  "Chapter ${index + 1}: $chapter".let { it + "\n" + "=".repeat(it.length) + "\n" }
}

for (title in titles) {
  println(title)
}

或更具可读性：

val chapters = arrayOf("Basic syntax", "Idioms", "Kotlin by example", "Coding conventions")

val titles = chapters
  .mapIndexed { index, chapter ->
    "Chapter ${index + 1}: $chapter"
      .let { title ->
        buildString {
          append(title)
          append("\n")
          append("=".repeat(title.length))
          append("\n")
        }
      }
  }

for (title in titles) {
  println(title)
}

Answer 3

@lukas.j 的解决方案的进一步简化变体可能如下所示：

val chapters = arrayOf("Basic syntax", "Idioms", "Kotlin by example", "Coding conventions")
val titles = chapters
    .mapIndexed { index, chapter ->
        buildString {
            append("Chapter ${index + 1}: $chapter")
            append('\n')
            repeat(length - 1) { append('=') }
            append("\n")
        }
    }
      
titles.forEach { println(it) }

Answer 4

只是另一个版本，向我们的好朋友致敬 print，您可以在同一行上继续打印字符。（并不是说这是最好的方式，但了解您的选择是件好事！）

chapters.forEachIndexed { i, title ->
    val heading = "Chapter ${i + 1}: $title"
    println(heading)
    repeat(heading.length) { print('=') }
    print("\n\n")
}

所以它的组织方式与格式一样 - 打印您的 header，打印您的下划线，然后打印您需要的任何行分隔符。我认为这很容易阅读和使用（并且可能会成为一个很好的独立功能）。

如果您不喜欢 ===== 行的分隔符被卷入最后的分隔符格式行，您可以随时执行类似

的操作

repeat(heading.length) { print('=') }.also { print("\n") } // or println()

如果你愿意的话。或者 run 或 let，没关系，also 只是读起来像“哦，最后是这个”

Kotlin：如何通过将字符重复给定次数来创建字符串

Kotlin: How to create a string by repeating a character a given number of times

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string

kotlin

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