title: How to check whether a string contains lowercase letter, uppercase letter, special character and digit?
body: <p>I've been Googling a lot and I didn't find an answer for my question:</p>
  
  <p>How can I check with a regular expression whether a string contains at least one of each of these:</p>
  
  <ul>
  <li>Uppercase letter</li>
  <li>Lowercase letter</li>
  <li>Digit</li>
  <li>Special Character: <code>~`!@#$%^&amp;*()-_=+\|[{]};:'",&lt;.&gt;/?</code></li>
  </ul>
  
  <p>So I need at least a capital letter <em>and</em> at least a small letter <em>and</em> at least a digit <em>and</em> at least a special character.</p>
  
  <p>I'm sure the answer is very simple, but I can't find it. Any help is greatly appreciated.</p>