Converting longitude latitude degrees to miles in Java

How do you convert degrees (longitude latitude) to miles in Java?

For 开发者_高级运维example if I want to move longitude by 69.11 miles, I add 1 degree. Do I do simple calculation or should I use some kind of API.

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From http://www.meridianworlddata.com/Distance-Calculation.asp:

Improved approximate distance in miles:

    sqrt(x * x + y * y)

where x = 69.1 * (lat2 - lat1)
and y = 69.1 * (lon2 - lon1) * cos(lat1/57.3) 

There were a few other good sites on the google.