code: private static void applyOverrides() {
          // Get the appropriate InputStream to read overrides from, if any.
          InputStream stream = getContentTypesPropertiesStream();
          if (stream == null) {
              return;
          }
  
          try {
              try {
                  // Read the properties file...
                  Properties overrides = new Properties();
                  overrides.load(stream);
                  // And translate its mapping to ours...
                  for (Map.Entry<Object, Object> entry : overrides.entrySet()) {
                      String extension = (String) entry.getKey();
                      String mimeType = (String) entry.getValue();
                      add(mimeType, extension);
                  }
              } finally {
                  stream.close();
              }
          } catch (IOException ignored) {
          }
      }
docs: This isn't what the RI does. The RI doesn't have hard-coded defaults, so supplying your
  own "content.types.user.table" means you don't get any of the built-ins, and the built-ins
  come from "$JAVA_HOME/lib/content-types.properties".