Construct URL as
new URL("http", "10:100::1234", 9999, "/index.html");
and access toExternalForm() or toString() then output is coming as ..
http://10:100::1234:9999/index.html

Here we cant say whether 9999 is a port no or part of the host name.

This is coming on Solaris 8 with build 59.

How to reproduce it:

Execute the below pasted test class..

import java.net.*;

public class TestURL {

public static void main(String[] args) {


        try {
           

                URL u3 = new URL("http", "10:100::1234", 9999, "/index.html");

                System.out.println("ToString u3 : " + u3.toString());
                System.out.println("Toexternal form u3 : " + u3.toExternalForm());

        } catch(Exception exp) {

                exp.printStackTrace();
        }
}

}// End of class