Extract hexadecimal values from a percent encoded URL

Question

Let's say for example i have URL containing the following percent encoded character : %80
It is obviously not an ascii character.
How would it be possible to convert this value to the corresponding hex string in Java. i tried the following with no luck.Result should be 80.

    public static void main(String[] args) {
        System.out.print(byteArrayToHexString(URLDecoder.decode("%80","UTF-8").getBytes()));
    }
    public static String byteArrayToHexString(byte[] bytes)
    {
      StringBuffer buffer = new StringBuffer();
      for(int i=0; i<bytes.length; i++)
      {
        if(((int)bytes[i] & 0xff) < 0x10)
        buffer.append("0");
        buffer.append(Long.toString((int) bytes[i] & 0xff, 16));
      }
      return buffer.toString();
  }

Answer 1

The best way to deal with this is to parse the url using either java.net.URL or java.net.URI , and then use the relevant getters to extract the components that you require. These will take care of decoding any %-encoded portions in the appropriate fashion.

The problem with your current idea is that %80 does not represent "80" , or 80 . Rather it represents a byte that further needs to be interpreted in the context of the character encoding of the URL. And if the encoding is UTF-8, then the %80 needs to be followed by one or two more %-encoded bytes ... otherwise this is a malformed UTF-8 character representation.

Answer 2

I don't really see what you are trying. However, I'll give it a try.

• When you have got this String: "%80" and you want to got the string "80" , you can use this:

   String str = "%80"; String hex = str.substring(1); // Cut off the '%' 

• If you are trying to extract the value 0x80 (which is 128 in decimal) out of it:

   String str = "%80"; String hex = str.substring(1); // Cut off the '%' int value = Integer.parseInt(hex, 16); 

• If you are trying to convert an int to its hexadecimal representation use this:

   String hexRepresenation = Integer.toString(value, 16);