title: regular expression for not allowing white space at start
body: <p>A regular expression to allow only alphabets and numbers and spaces only in between alphabets with a maximum size of <strong>20</strong>.</p>
  
  <p><code>([a-zA-Z0-9]+([\\s][a-zA-Z0-9]+)*){0,20}</code>. </p>
  
  <p>This does not allow white space at start, but it is not checking the max size condition. How can  I change this regular expression?</p>