title: Replacing one character with another in a string
body: <p>I have a data like below:</p>
  
  <p><code>A:B:C:D</code></p>
  
  <p>and I want to replace the <code>C</code> with data (say, <code>Z</code>) so that it may look like</p>
  
  <p><code>A:B:Z:D</code></p>
  
  <p>How can I do it?</p>