title: UnknownFormatConversionException is caused by symbol '%' in String.format()
body: <pre><code>String template = "%s and '%'";
  String result = String.format(template, "my string");
  System.out.println(result);
  </code></pre>
  
  <p><strong>Expected</strong>: </p>
  
  <pre><code>my string and '%'
  </code></pre>
  
  <p><strong>But result is</strong>:</p>
  
  <pre><code>java.util.UnknownFormatConversionException: Conversion = '''
  </code></pre>
  
  <p><strong>Why?</strong> How to correctly declared the sequence <code>'%'</code> so that it's ignored by <code>String.format()</code>?</p>