LocationTech

Java port of the Proj.4 library for coordinate reprojection

GeoTrellis is a geographic data processing engine for high performance applications.

The JTS Topology Suite is a Java library for creating and manipulating vector geometry.

GeoWave provides geospatial and temporal indexing on top of Accumulo, HBase, BigTable, Cassandra, and DynamoDB

Geospatial Raster support for Spark DataFrames

GeoMesa is a suite of tools for working with big geo-spatial data in a distributed fashion.

uDig parent project containing all core components. More plugins can be found in community repos: http://github.com/uDig-Community

LocationTech Spatial4j: A Geospatial Library for Java

GeoGig project

Geoff project at LocationTech

LocationTech SFCurve is a Scala library for the creation, transformation, and querying of space-filling curves

Geobench project