code: private static HashMap<String, String> loadMappings() {
  
          HashMap<String, String> mimeTypeToExtensionMap =
                  new HashMap<String, String>();
  
          // First, check the user's home directory.
  
          String fileSep = System.getProperty("file.separator");
          StringBuffer buf = new StringBuffer();
  
          buf.append(System.getProperty("user.home"));
          buf.append(fileSep);
          buf.append(".mime.types");
  
          loadMIMETypesFile(buf.toString());
  
          // Now, check every directory in the classpath.
  
          String pathSep = System.getProperty("path.separator");
          String[] pathComponents = pathSep.split(" ");
          int i;
  
          for (i = 0; i < pathComponents.length; i++) {
              buf.setLength(0);
              buf.append(pathComponents[i]);
              buf.append(fileSep);
              buf.append("mime.types");
  
              loadMIMETypesFile(buf.toString());
          }
  
          // Finally, load the resource bundle.
  
          ResourceBundle bundle = ResourceBundle.getBundle(MIME_MAPPINGS_BUNDLE);
          for (Enumeration<?> e = bundle.getKeys(); e.hasMoreElements();) {
              String type = (String) e.nextElement();
              try {
                  String[] extensions = bundle.getString(type).split(" ");
  
                  if (mimeTypeToExtensionMap.get(type) == null) {
                      logger.debug("Internal: " + type + " -> \"" + extensions[0]
                              + "\"");
                      mimeTypeToExtensionMap.put(type, extensions[0]);
                  }
              }
  
              catch (MissingResourceException ex) {
                  logger.error("While reading internal bundle \""
                                    + MIME_MAPPINGS_BUNDLE
                                    + "\", got unexpected error on key \"" + type
                                    + "\"",
                            ex);
              }
          }
          return mimeTypeToExtensionMap;
      }
docs: Load the MIME type mappings into memory.