title: Java - Find Regex to match in String
body: <p>I need some help because i'm junior in Java and after some research on the web
  I can't find a solution.
  So my problem:</p>
  
  <pre><code>String str : size="A4"
  </code></pre>
  
  <p>I would like to extract 'A4' with a regex by giving the word "size" in the regex.
  How can I do ? </p>