Check URL Validity

Question

Hello, I'm trying to figure out how to check the validity of a URL. I have wrote something, but it's not exactly what I want. Here is what I have:
     public boolean URLCheck(String checkme) {
          if((checkme.contains("http://") || checkme.contains("https://") ||
                    checkme.contains("ftp://")) && (checkme.contains(".edu") ||
                    checkme.contains(".com") || checkme.contains(".net") ||
                    checkme.contains(".org"))) {
               return true;
          else{
               output.setText("Bad URL.");
               return false;
     }This is obviously very flawed, it only checks the protocol and the end of the server address (com,org,net,etc...).
I would like to write a piece of code that could check if the URL is in this format, but I'm not sure where to begin.
< url > ::= < protocol >://< server_address >/< local_address >
< protocol > ::= http | https | ftp
< server_address > ::= < host >.< domain > | < host>.< domain >:< port >
< host > ::= < alphanumeric_character_string >
< domain > ::= < alphanumeric_character_string > |
               < alphanumeric_character_string >.< domain >
< port > ::= < numerical_string >
< local_address > ::= ~< login_name >/< location > | < location >
< location > ::= < null_string > | < file_name > |
                 < path >/ | < path >/< file_name >
< path > ::= < directory_name > | < directory_name >/< path >I'm not asking to have the code written for me, but I was wondering if someone could tell me how I could go about doing something like this.
Thank you in advance!

Answer 1

Thank you, here is what I tried:
     public void grabURLContents(String contents) throws Exception {
          try {
               URL inputFile = new URL(contents);
               BufferedReader in = new BufferedReader(
                              new InputStreamReader(
                              inputFile.openStream()));
               String inputLine, storage = "";
               while ((inputLine = in.readLine()) != null)
                   storage += inputLine +"\n";
               output.setText(storage);
               in.close();
          catch(Exception e) { output.setText("BAD URL: \n" + e); }
     }The only problem with this is: when I enter a url that obviously doesn't exist such as http://awdawfagasegr.com it still prints the html contents of my ISP's "Page not Found" page. Is there any way to prevent this?
Thank you for your help by the way. Sorry if I seem very ignorant, I am not familiar with Java's URL class.