Class OrdinateFormat

1	/*
2	* Copyright (c) 2019 Martin Davis.
3	*
4	* All rights reserved. This program and the accompanying materials
5	* are made available under the terms of the Eclipse Public License 2.0
6	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8	* and the Eclipse Distribution License is available at
9	*
10	* http://www.eclipse.org/org/documents/edl-v10.php.
11	*/
12
13	package org.locationtech.jts.io;
14
15	import java.text.DecimalFormat;
16	import java.text.DecimalFormatSymbols;
17
18	/**
19	* Formats numeric values for ordinates
20	* in a consistent, accurate way.
21	* <p>
22	* The format has the following characteristics:
23	* <ul>
24	* <li>It is consistent in all locales (in particular, the decimal separator is always a period)
25	* <li>Scientific notation is never output, even for very large numbers.
26	* This means that it is possible that output can contain a large number of digits.
27	* <li>The maximum number of decimal places reflects the available precision
28	* <li>NaN values are represented as "NaN"
29	* <li>Inf values are represented as "Inf" or "-Inf"
30	* </ul>
31	*
32	* @author mdavis
33	*
34	*/
35	public class OrdinateFormat
36	{
37	/**
38	* The output representation of {@link Double#POSITIVE_INFINITY}
39	*/
40	public static final String REP_POS_INF = "Inf";
41
42	/**
43	* The output representation of {@link Double#NEGATIVE_INFINITY}
44	*/
45	public static final String REP_NEG_INF = "-Inf";
46
47	/**
48	* The output representation of {@link Double#NaN}
49	*/
50	public static final String REP_NAN = "NaN";
51
52	/**
53	* The maximum number of fraction digits to support output of reasonable ordinate values.
54	*
55	* The default is chosen to allow representing the smallest possible IEEE-754 double-precision value,
56	* although this is not expected to occur (and is not supported by other areas of the JTS code).
57	*/
58	public static final int MAX_FRACTION_DIGITS = 325;
59
60	/**
61	* The default formatter using the maximum number of digits in the fraction portion of a number.
62	*/
63	public static OrdinateFormat DEFAULT = new OrdinateFormat();
64
65	/**
66	* Creates a new formatter with the given maximum number of digits in the fraction portion of a number.
67	*
68	* @param maximumFractionDigits the maximum number of fraction digits to output
69	* @return a formatter
70	*/
71	public static OrdinateFormat create(int maximumFractionDigits) {
72	return new OrdinateFormat(maximumFractionDigits);
73	}
74
75	private DecimalFormat format;
76
77	/**
78	* Creates an OrdinateFormat using the default maximum number of fraction digits.
79	*/
80	public OrdinateFormat() {
81	format = createFormat(MAX_FRACTION_DIGITS);
82	}
83
84	/**
85	* Creates an OrdinateFormat using the given maximum number of fraction digits.
86	*
87	* @param maximumFractionDigits the maximum number of fraction digits to output
88	*/
89	public OrdinateFormat(int maximumFractionDigits) {
90	format = createFormat(maximumFractionDigits);
91	}
92
93	private static DecimalFormat createFormat(int maximumFractionDigits) {
94	// specify decimal separator explicitly to work in all locales
95	DecimalFormatSymbols symbols = new DecimalFormatSymbols();
96	symbols.setDecimalSeparator('.');
97	DecimalFormat format = new DecimalFormat("0", symbols);
98	format.setMaximumFractionDigits(maximumFractionDigits);
99	return format;
100	}
101
102	/**
103	* Returns a string representation of the given ordinate numeric value.
104	*
105	* @param ord the ordinate value
106	* @return the formatted number string
107	*/
108	public synchronized String format(double ord)
109	{
110	/**
111	* FUTURE: If it seems better to use scientific notation
112	* for very large/small numbers then this can be done here.
113	*/
114
115	if (Double.isNaN(ord)) return REP_NAN;
116	if (Double.isInfinite(ord)) {
117	return ord > 0 ? REP_POS_INF : REP_NEG_INF;
118	}
119	return format.format(ord);
120	}
121
122	}
123