What is a malformed URL and what problem occurs due to it ?

When you create an instance of the java.net.URL class, its constructor can throw a MalformedURLException.

This occurs when the URL is invalid.

A malformed URL exception is thrown when the URL cannot be correctly parsed.

It is not thrown, when :

• The host machine is down
• URL path points to a missing file

Common mistakes include : 

• leaving out a protocol (eg "www.microsoft.com" instead of "http//www.microsoft.com/")
• specifying an invalid protocol (eg "http: // www: //netscape.com")
• leaving out the ':' character (eg http// www.micrsoft.com/)

MalformedURLException will not be thrown if :

• host name is invalid (eg "http: //www.microsoft-rules-the-world.com")
• path is invalid (eg "http: //www.microsoft.com/company_secrets.htm")