searching for url in file

I have assignment that im stuck with.
Design a program that finds all hyperlinks of the form <a href="link">link text</a> on the address http://java.sun.com/index.html

I have already did the read and write its contents to a file. I am stuck at, how can i read contents that in the file, and know whether it is a url then return its url address. Any suggestions?

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