GenericUrl: improve the error message for malformed URLs

[alb-i986]

Let's say by mistake we pass a malformed URL to the constructor of GenericUrl.

new GenericUrl("http://example.com:8080http://example.com:8080");

Previously the line above used to throw the following exception:

java.lang.IllegalArgumentException: java.net.MalformedURLException: Error at index 4 in: "8080http:"

Not very helpful.

Whereas with this patch:

java.lang.IllegalArgumentException: Malformed URL: "http://example.com:8080http://example.com:8080/"

The exception thrown now clearly shows what was the faulty URL.
The user can therefore quickly figure out which URL needs to be fixed.

A lesson I learned today :)

[meltsufin]

There might be a risk of leaking sensitive data from the URL. So, I'm leaning towards the JDK deciding what the message should be.