String filePath = this.getClass().getResource("/").getPath();
filePath = filePath.replaceAll("\\/|"+Matcher.quoteReplacement("\\"),Matcher.quoteReplacement(File.separator));
System.out.println("filePath: " + filePath+"html" +File.separator+"56465");

 public static void main(String[] args){
        String filePath = this.getClass().getResource("/").getPath();
        filePath = filePath.replaceAll("\\", File.separator);
        System.out.println(filePath);
}