The Java Topology Suite (JTS) is a Java API that implements a core set of spatial data operations using an explicit precision model and robust geometric algorithms. JTS is intended to be used in the development of applications that support the validation, cleaning, integration and querying of spatial datasets.
JTS attempts to implement the OpenGIS Simple Features Specification (SFS) as accurately as possible. In some cases the SFS is unclear or omits a specification; in this case JTS attempts to choose a reasonable and consistent alternative. Differences from and elaborations of the SFS are documented in this specification.
There are many approaches to dealing with the problem of robustness in geometrical computation. Not surprisingly, most robust algorithms are substantially more complex and less performant than the non-robust versions. Fortunately, JTS is sensitive to robustness problems in only a few key functions (such as line intersection and the point-in-polygon test). There are efficient robust algorithms available for these functions, and these algorithms are implemented in JTS.
The obvious naive algorithm for intersection detection (comparing every segment with every other) has unacceptably slow performance. There is a large literature of faster algorithms for intersection detection. Unfortunately, many of them involve substantial code complexity. JTS tries to balance code simplicity with performance gains. It uses some simple techniques to produce substantial performance gains for common types of input data.