title: Kotlin: how to swap character in String
body: <p>I would like to swap a string from "abcde" to "bcdea". So I wrote my code as below in Kotlin</p>
  
  <pre><code>var prevResult = "abcde"
  var tmp = prevResult[0]
  
  for (i in 0..prevResult.length - 2) {
      prevResult[i] = prevResult[i+1]  // Error on preveResult[i]
  }
  
  prevResult[prevResult.length-1] = tmp // Error on preveResult[prevResult.lengt-1]
  </code></pre>
  
  <p>It errors out as stated above comment line. What did I do wrong? How could I fix this and get what I want?</p>