com.vividsolutions.jts.index.kdtree

Class KdTree

java.lang.Object

com.vividsolutions.jts.index.kdtree.KdTree

public class KdTree
extends Object

An implementation of a 2-D KD-Tree. KD-trees provide fast range searching on point data.

This implementation supports detecting and snapping points which are closer than a given distance tolerance. If the same point (up to tolerance) is inserted more than once, it is snapped to the existing node. In other words, if a point is inserted which lies within the tolerance of a node already in the index, it is snapped to that node. When a point is snapped to a node then a new node is not created but the count of the existing node is incremented. If more than one node in the tree is within tolerance of an inserted point, the closest and then lowest node is snapped to.

Author:

David Skea, Martin Davis

Constructor Summary

Constructors

Constructor and Description
KdTree() Creates a new instance of a KdTree with a snapping tolerance of 0.0.
KdTree(double tolerance) Creates a new instance of a KdTree, specifying a snapping distance tolerance.

Method Summary

Methods

Modifier and Type	Method and Description
KdNode	insert(Coordinate p) Inserts a new point in the kd-tree, with no data.
KdNode	insert(Coordinate p, Object data) Inserts a new point into the kd-tree.
boolean	isEmpty() Tests whether the index contains any items.
List	query(Envelope queryEnv) Performs a range search of the points in the index.
void	query(Envelope queryEnv, KdNodeVisitor visitor) Performs a range search of the points in the index and visits all nodes found.
void	query(Envelope queryEnv, List result) Performs a range search of the points in the index.
static Coordinate[]	toCoordinates(Collection kdnodes) Converts a collection of KdNodes to an array of Coordinates.
static Coordinate[]	toCoordinates(Collection kdnodes, boolean includeRepeated) Converts a collection of KdNodes to an array of Coordinates, specifying whether repeated nodes should be represented by multiple coordinates.

Methods inherited from class java.lang.Object

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

Constructor Detail

KdTree

public KdTree()

Creates a new instance of a KdTree with a snapping tolerance of 0.0. (I.e. distinct points will not be snapped)

KdTree

public KdTree(double tolerance)

Creates a new instance of a KdTree, specifying a snapping distance tolerance. Points which lie closer than the tolerance to a point already in the tree will be treated as identical to the existing point.

Parameters:

tolerance - the tolerance distance for considering two points equal

Method Detail

toCoordinates

public static Coordinate[] toCoordinates(Collection kdnodes)

Converts a collection of KdNodes to an array of Coordinates.

Parameters:

kdnodes - a collection of nodes

Returns:

an array of the coordinates represented by the nodes

toCoordinates

public static Coordinate[] toCoordinates(Collection kdnodes,
                         boolean includeRepeated)

Converts a collection of KdNodes to an array of Coordinates, specifying whether repeated nodes should be represented by multiple coordinates.

Parameters:

kdnodes - a collection of nodes

includeRepeated - true if repeated nodes should be included multiple times

Returns:

an array of the coordinates represented by the nodes

isEmpty

public boolean isEmpty()

Tests whether the index contains any items.

Returns:

true if the index does not contain any items

insert

public KdNode insert(Coordinate p)

Inserts a new point in the kd-tree, with no data.

Parameters:

p - the point to insert

Returns:

the kdnode containing the point

insert

public KdNode insert(Coordinate p,
            Object data)

Inserts a new point into the kd-tree.

Parameters:

p - the point to insert

data - a data item for the point

Returns:

returns a new KdNode if a new point is inserted, else an existing node is returned with its counter incremented. This can be checked by testing returnedNode.getCount() > 1.

query

public void query(Envelope queryEnv,
         KdNodeVisitor visitor)

Performs a range search of the points in the index and visits all nodes found.

Parameters:

queryEnv - the range rectangle to query

a - visitor to visit all nodes found by the search

query

public List query(Envelope queryEnv)

Performs a range search of the points in the index.

Parameters:

queryEnv - the range rectangle to query

Returns:

a list of the KdNodes found

query

public void query(Envelope queryEnv,
         List result)

Performs a range search of the points in the index.

Parameters:

queryEnv - the range rectangle to query

result - a list to accumulate the result nodes into