oracle.spatial.geometry

Class Chain

java.lang.Object

oracle.spatial.geometry.Chain

public final class Chain
extends java.lang.Object

Provides an efficient double-ended list of vertices, which can be referenced by either end. The following operations are provided:

1. Coordinates can be inserted onto either end in O(1) time
2. Two chains can be appended into one longer chain.
3. The time to build a chain of n vertices is O(n log n) time through any combination of inserting vertices and appending chains.

The chain also supports storing lists of Chains with a Chain --- this is used to store polygons with holes (the chain itself as the exterior boundary, the list of chains as holes). When chains are merged the corresponding lists will be merged in an arbitrary order. Nothing in this class prevents arbitrary nesting, but current usage in Buffer does not have holes within holes, and any such would symptomatic of a bug in buffer.

*** Note that the metadata add & get routines hold onto list objects and return live list objects, and that the routines may return null lists ***. This bit of bad API design is to avoid large blow-ups when lists of holes are passed and merged through multiple chain objects.

Creation of a chain returns the two endpoints (two separate objects). Each end is indexed with "0" being the coordinate closest to that end (a newly added vertex on an end becomes the new 0th coordinate for that end), and the coordinate on the opposite end being at index (size - 1).

Since:

August 2012

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Chain.AccurateSum Accurately accumulate a summation.
static class	Chain.CenterPoint Abusing subclassing --- this is used to store the centers of circular arcs in Chain.

Method Summary

Modifier and Type	Method and Description
java.lang.String	toString()
java.lang.String	WKT() Debugging only
java.lang.String	WKTList() Debugging only

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

WKT

public java.lang.String WKT()

Debugging only

Returns:

Chain as a LINESTRING, arcs expanded into linears. Metadata is ignored.

WKTList

public java.lang.String WKTList()

Debugging only

Returns:

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object