Kotlin:如何通过重复给定次数的字符来创建字符串

Question

我正试图在标题下打印一条线。意思是这一行和标题的长度是一样的。我尝试了几种方法，我认为这是最接近的，但它给我的结果是不正确的。

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

是否有一种简单的方法通过重复一个字符来初始化一个字符串？

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

@lukas.j解决方案的进一步简化可能如下所示：

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 3

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)
}

或更易读：

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)
}