title: Use Java and RegEx to convert casing in a string
body: <p>Problem: Turn </p>
  
  <pre><code>"My Testtext TARGETSTRING My Testtext" 
  </code></pre>
  
  <p>into </p>
  
  <pre><code>"My Testtext targetstring My Testtext"
  </code></pre>
  
  <p>Perl supports the "\L"-operation which can be used in the replacement-string. </p>
  
  <p>The Pattern-Class does not support this operation:</p>
  
  <blockquote>
    <p>Perl constructs not supported by this class:
    [...] 
    The preprocessing operations \l \u, \L, and \U.
    <a href="https://docs.oracle.com/javase/10/docs/api/java/util/regex/Pattern.html" rel="noreferrer">https://docs.oracle.com/javase/10/docs/api/java/util/regex/Pattern.html</a></p>
  </blockquote>