This project is a direct port of Proj.NET. The original project is located here: http://projnet.codeplex.com/

ProjJava performs point-to-point coordinate conversions between geodetic coordinate systems for use in for example Geographic Information Systems (GIS) or GPS applications. The spatial reference model used adheres to the Simple Features specification.

• Datum transformations
• Geographic, Geocentric, and Projected coordinate systems
• Compatible with Java and the Android plattform
• Converts coordinate systems to/from Well-Known Text (WKT) and to XML

• Mercator
• Transverse Mercator
• Albers
• Lambert Conformal
• Krovak

For an introduction to spatial reference systems see here