Class GeometryCollectionIterator

1
2
3	/*
4	* Copyright (c) 2016 Vivid Solutions.
5	*
6	* All rights reserved. This program and the accompanying materials
7	* are made available under the terms of the Eclipse Public License 2.0
8	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
9	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
10	* and the Eclipse Distribution License is available at
11	*
12	* http://www.eclipse.org/org/documents/edl-v10.php.
13	*/
14	package org.locationtech.jts.geom;
15
16	import java.util.Iterator;
17	import java.util.NoSuchElementException;
18
19	/**
20	* Iterates over all {@link Geometry}s in a {@link Geometry},
21	* (which may be either a collection or an atomic geometry).
22	* The iteration sequence follows a pre-order, depth-first traversal of the
23	* structure of the <code>GeometryCollection</code>
24	* (which may be nested). The original <code>Geometry</code> object is
25	* returned as well (as the first object), as are all sub-collections and atomic elements.
26	* It is simple to ignore the intermediate <code>GeometryCollection</code> objects if they are not
27	* needed.
28	*
29	*@version 1.7
30	*/
31	public class GeometryCollectionIterator implements Iterator {
32
33	/**
34	* The <code>Geometry</code> being iterated over.
35	*/
36	private Geometry parent;
37	/**
38	* Indicates whether or not the first element
39	* (the root <code>GeometryCollection</code>) has been returned.
40	*/
41	private boolean atStart;
42	/**
43	* The number of <code>Geometry</code>s in the the <code>GeometryCollection</code>.
44	*/
45	private int max;
46	/**
47	* The index of the <code>Geometry</code> that will be returned when <code>next</code>
48	* is called.
49	*/
50	private int index;
51	/**
52	* The iterator over a nested <code>Geometry</code>, or <code>null</code>
53	* if this <code>GeometryCollectionIterator</code> is not currently iterating
54	* over a nested <code>GeometryCollection</code>.
55	*/
56	private GeometryCollectionIterator subcollectionIterator;
57
58	/**
59	* Constructs an iterator over the given <code>Geometry</code>.
60	*
61	*@param parent the geometry over which to iterate; also, the first
62	* element returned by the iterator.
63	*/
64	public GeometryCollectionIterator(Geometry parent) {
65	this.parent = parent;
66	atStart = true;
67	index = 0;
68	max = parent.getNumGeometries();
69	}
70
71	/**
72	* Tests whether any geometry elements remain to be returned.
73	*
74	* @return true if more geometry elements remain
75	*/
76	public boolean hasNext() {
77	if (atStart) {
78	return true;
79	}
80	if (subcollectionIterator != null) {
81	if (subcollectionIterator.hasNext()) {
82	return true;
83	}
84	subcollectionIterator = null;
85	}
86	if (index >= max) {
87	return false;
88	}
89	return true;
90	}
91
92	/**
93	* Gets the next geometry in the iteration sequence.
94	*
95	* @return the next geometry in the iteration
96	*/
97	public Object next() {
98	// the parent GeometryCollection is the first object returned
99	if (atStart) {
100	atStart = false;
101	if (isAtomic(parent))
102	index++;
103	return parent;
104	}
105	if (subcollectionIterator != null) {
106	if (subcollectionIterator.hasNext()) {
107	return subcollectionIterator.next();
108	}
109	else {
110	subcollectionIterator = null;
111	}
112	}
113	if (index >= max) {
114	throw new NoSuchElementException();
115	}
116	Geometry obj = parent.getGeometryN(index++);
117	if (obj instanceof GeometryCollection) {
118	subcollectionIterator = new GeometryCollectionIterator((GeometryCollection) obj);
119	// there will always be at least one element in the sub-collection
120	return subcollectionIterator.next();
121	}
122	return obj;
123	}
124
125	private static boolean isAtomic(Geometry geom)
126	{
127	return ! (geom instanceof GeometryCollection);
128	}
129
130	/**
131	* Removal is not supported.
132	*
133	* @throws UnsupportedOperationException This method is not implemented.
134	*/
135	public void remove() {
136	throw new UnsupportedOperationException(getClass().getName());
137	}
138	}
139
140