PApplet line 7475 or thereabouts

extract.java

/**
   * Return a full path to an item in the data folder as a File object.
   * See the dataPath() method for more information.
   */
  public File dataFile(String where) {
    // isAbsolute() could throw an access exception, but so will writing
    // to the local disk using the sketch path, so this is safe here.
    File why = new File(where);
    if (why.isAbsolute()) return why;

    String jarPath =
      getClass().getProtectionDomain().getCodeSource().getLocation().getPath();
    if (jarPath.contains("Contents/Java/")) {
      // The path will be URL encoded (%20 for spaces) coming from above
      // http://code.google.com/p/processing/issues/detail?id=1073
      File containingFolder = new File(urlDecode(jarPath)).getParentFile();
      File dataFolder = new File(containingFolder, "data");
      return new File(dataFolder, where);
    }
    // Windows, Linux, or when not using a Mac OS X .app file
    return new File(sketchPath + File.separator + "data" + File.separator + where);
  }