com.revolsys.jts.operation.union

Class UnaryUnionOp

java.lang.Object

com.revolsys.jts.operation.union.UnaryUnionOp

public class UnaryUnionOp
extends Object

Unions a Collection of Geometrys or a single Geometry (which may be a GeoometryCollection) together. By using this special-purpose operation over a collection of geometries it is possible to take advantage of various optimizations to improve performance. Heterogeneous GeometryCollections are fully supported.

The result obeys the following contract:

• Unioning a set of Polygons has the effect of merging the areas (i.e. the same effect as iteratively unioning all individual polygons together).
• Unioning a set of LineStrings has the effect of noding and dissolving the input linework. In this context "fully noded" means that there will be an endpoint or node in the result for every endpoint or line segment crossing in the input. "Dissolved" means that any duplicate (i.e. coincident) line segments or portions of line segments will be reduced to a single line segment in the result. This is consistent with the semantics of the Geometry.union(Geometry) operation. If merged linework is required, the LineMerger class can be used.
• Unioning a set of Points has the effect of merging all identical points (producing a set with no duplicates).

UnaryUnion always operates on the individual components of MultiGeometries. So it is possible to use it to "clean" invalid self-intersecting MultiPolygons (although the polygon components must all still be individually valid.)

Author:

mbdavis

Constructor Summary

Constructors

Constructor and Description
UnaryUnionOp()

Method Summary

Methods

Modifier and Type	Method and Description
static Geometry	union(Collection<? extends Geometry> geometries) Computes the geometric union of a Collection of Geometrys.
static Geometry	union(Collection<? extends Geometry> geometries, GeometryFactory geometryFactory) Computes the geometric union of a Collection of Geometrys.
static Geometry	union(Geometry... geometries) Constructs a unary union operation for a Geometry (which may be a GeometryCollection).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

UnaryUnionOp

public UnaryUnionOp()

Method Detail

union

public static Geometry union(Collection<? extends Geometry> geometries)

Computes the geometric union of a Collection of Geometrys.

Parameters:

geoms - a collection of geometries

Returns:

the union of the geometries, or null if the input is empty

union

public static Geometry union(Collection<? extends Geometry> geometries,
             GeometryFactory geometryFactory)

Computes the geometric union of a Collection of Geometrys. If no input geometries were provided but a GeometryFactory was provided, an empty GeometryCollection is returned.

Parameters:

geoms - a collection of geometries

geometryFactory - the geometry factory to use if the collection is empty

Returns:

the union of the geometries, or an empty GEOMETRYCOLLECTION

union

public static Geometry union(Geometry... geometries)

Constructs a unary union operation for a Geometry (which may be a GeometryCollection).

Parameters:

geom - a geometry to union

Returns:

the union of the elements of the geometry or an empty GEOMETRYCOLLECTION