title: Class 'String' has no instance method '-'
body: <p>What method instead of method '-' in String type?
  I want to remove an element of 'ngang'. This is data of 'ngang':</p>
  <pre><code>String ngang ='';
  for (int i =0; i &lt;x; i++){
  ngang +='*';}
  </code></pre>
  <p><a href="https://i.stack.imgur.com/oD3J4.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oD3J4.jpg" alt="enter image description here" /></a></p>