Checking a phone number

Problem:
To check if a phone number can be called programmatically
- By calling I mean dialling out the number and see if the connection
to that number responds

Limitations:
Solution needs to be in Java

Questions:
1. Has anybody worked on this kind of requirement?
2. Does JTAPI give a solution for this requirement?
3. Which vendor's implementation of JTAPI is better?
4. What should one lookout when using a vendor's implementation of
JTAPI?

Let me know your inputs.

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