A tiny geography library in Java: map projections, coordinate conversion etc. Mostly refactored from Nasa WorldWind.
Example usage for converting geographic coordinates into cartesian coordinates:
ProjectionMercator p = new ProjectionMercator();
double lat = 13.7;
double lon = 137.7;
//from a mercator projection to cartesian coordinates (assuming WGS84)
double[] xy = p.geographicToCartesian(lat, lon);
double[] latlon = p.cartesianToGeographic(xy);
//from lat/lon to UTM coordinates and back
int utmZone = 1;
p = new ProjectionUTM(1);
//...and so on 
You can use this project as a dependency like so:
repositories {
maven{url 'https://dl.bintray.com/lukehb/137-geo'} //hosted on bintray
}
dependencies {
compile 'onethreeseven:geo:0.0.4'
}