title: How to check if a given Regex is valid?
body: <p>I have a little program allowing users to type-in some regular expressions. afterwards I like to check if this input is a <strong>valid</strong> regex or not.</p>
  
  <p>I'm wondering if there is a build-in method in Java, but could not find such jet.</p>
  
  <p>Can you give me some advice?</p>