title: "Error: Could not find or load main class" - Visibility exception
body: <p>I have the following code, which needs to be run by the HackerRank automated validator.</p>
  
  <pre><code>package stringrev;
  
  import java.util.Scanner;
  
  class str {
    public static void main(String[] args) {
      Scanner in=new Scanner(System.in);
      int k=in.nextInt()+1;
      for(int i=0;i&lt;=k;i++)
      {
        StringBuffer a=new StringBuffer(in.nextLine());
        StringBuffer b=a.reverse();
        System.out.println(b);
      }
    }
  }
  </code></pre>
  
  <p>This code is working fine on my compiler but while uploading to Hacker Rank it shows an error:</p>
  
  <blockquote>
    <p>Error: Could not find or load main class str</p>
  </blockquote>
  
  <p>What does that mean?</p>