title: Why am I geting a blank when I run this string funtion in Kotlin?
body: <p>So I was solving a problem that required me to put unique characters in a string without using a data structure.</p>
  <pre><code>fun main(){
      val s1 = &quot;fhfnfnfjuw&quot;
      val s2 = &quot;Osayuki&quot;
      val s3 = &quot;Raymond&quot;
      val s4 = &quot;Aseosa&quot;
  
    uniqueChar(s1)
  }
  
  
  fun uniqueChar(s: String){
      val updatedString = &quot;&quot;
      s.forEach {c -&gt;
          if (!updatedString.contains(c)){
              updatedString.plus(c)
          }
      }
      println(updatedString)
  
  }
  </code></pre>
  <p>And getting this error
  <a href="https://i.stack.imgur.com/t7wcc.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/t7wcc.jpg" alt="enter image description here" /></a></p>
  <p>I'm not sure what's going on and why I'm getting a blank. I'm sure it's an easy fix, but I can't see it. Any help is appreciated.</p>