But I cannot be 100% sure on that the fetched link...
SHORT ANSWER
You will NEVER be sure.
LONG ANSWER
For a given random HTML page, you want to find the "Contact Us" link. This kind of work is trivial for a human. It represents a big challenge for a computer.
I can see some options in your case:
Option 1: Crowd sourcing
- Fetch all the website urls you want the "Contact Us" information
- Send them to a crowd service platform asking real people to find the information for you (Rapidworkers.com, Crowdsource.com, Clickworker.com, Amazon Mechanical Turk, microworkers.com)
Check if the platform offer an API.
+ work done by human
+ dynamically adapt to unknown pattern
- cost money
- We suck at repetitive tasks
Option 2: IA (patten searching)
- Train an IA for extracting the information
- Then through at it your websites
Have a look at Weka for instance or Java-ML.
+ Automated task
+ Can perform a repetitive task long time
- May take time to built a robust solution
- Risk of false positive or complete miss
Option 3: Use Jsoup
- Carefully study the pattern of the websites you target
- Tell Jsoup to find the pattern you have detected
This option is a never ending task. You'll have to always feed Jsoup with new patterns. I suggest you having a monitoring system telling you when website escapes any known pattern.
+ Automated task
+ Can perform a repetitive task long time
- Take time for studying, discovering, adding new patterns
- Risk of false positive or complete miss
Option 4: A mix of the three above options
You can have the three options working on the websites you target.
+ Reduce chances of false positive or complete misses
+ More confident final result
- Take time for studying, discovering, adding new patterns
- Cost money