Java URLDecoder decode Percentage Symbol as error

Question

I need to allow user to input various special characters, so i use the java URLDeacoder.decode() method, i tested using println. There is no problem with other special character except this Percentage symbol, it has error during execute. Why is that? I understand that % is being used for URL encoding, is this the reason?

java.lang.IllegalArgumentException: URLDecoder: Incomplete trailing escape (%) pattern

System.out.println(URLDecoder.decode("%", "UTF-8"));

Answer 1

Despite their names, URLEncoder/Decoder are for encoding POST arguments, not URLs. See @fge's remarks below.

The way to encode a URL is with the URL and URI classes.

I'm curious as to how you acquired an undecoded URL in the first place.