title: java.util.regex.PatternSyntaxException: Illegal repetition
body: <p>I am parsing many txt files with regex engine in Java; while nothing happened with many txt files, with one following exception arise:</p>
  
  <pre><code>Exception in thread "main" java.util.regex.PatternSyntaxException: 
  Illegal repetition near index 1
  b {en}http //fas org/sgp/crs/nuke/rs22542 pdf
  </code></pre>
  
  <p>The matching pattern is obtained looping on a set of strings computed at runtime, and the program is removing each matched pattern from text with <code>replaceAll()</code> but fails when pattern is non ordinary string <code>b {en}http //fas org/sgp/crs/nuke/rs22542 pdf</code>.</p>
  
  <p>What does it mean? How can I fix it or let compiler ignore this error?</p>