Java code for WGS84 to Google map position and back

Tile utility code in Java on mapki.com (great resource for google map developers)

Here are the functions in JavaSCript ... As extracted from OpenLayers

function toMercator (lon, lat) {
  var x = lon * 20037508.34 / 180;
  var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
  y = y * 20037508.34 / 180;

  return [x, y];
  }

function inverseMercator (x, y) {
  var lon = (x / 20037508.34) * 180;
  var lat = (y / 20037508.34) * 180;

  lat = 180/Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180)) - Math.PI / 2);

  return [lon, lat];
  }

Fairly straightforward to convert to Java

GeoTools has code to transform to and from about any coordinate system you could imagine, and among them also Google Map's. It's also open source. However, it should also be pointed out that GeoTools is a large library, so if you're looking something small, quick and easy, it's likely not the way to go.

I would highly recommend it though if you're going to do other GIS/coordinate transformations, etc. as well.

If you use GeoTools or something similar, you might also be interested in knowing that the Google Map coordinate system is called EPSG 3785.