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1
19 package jcckit.util;
20
21
26 class FormatElement {
27
28 static final String  DESCRIPTORS = "doxfeEgG";
29 private static final String INT_DESCRIPTORS = "dox";
30 private static final int INT_DESCRIPTOR = 0;
31 private static final int FLOAT_DESCRIPTOR = 1;
32
38 private static final double power(double x, int n) {
39 return n < 0 ? 1.0 / power2(x, -n) : power2(x, n);
40 }
41
42
43 private static final double power2(double x, int n) {
44 switch (n) {
45 case 0: return 1;
46 case 1: return x;
47 default:
48 double p = power2(x, n / 2);
49 return p * p * power2(x, n % 2);
50 }
51 }
52
53 private final char _descriptor;
54 private final int _descriptorType;
55 private final double _tenToPrecision;
56 private boolean _decimalPoint;
57 private boolean _flushLeft;
58 private boolean _leadingZeros;
59 private boolean _alwaysSign;
60 private int _width;
61 private int _precision;
62
63
64 FormatElement(String formatString) {
65 int len = formatString.length() - 1;
66 _descriptor = formatString.charAt(len);
67 if (DESCRIPTORS.indexOf(_descriptor) < 0) {
68 throw new IllegalArgumentException ("Format element '" + formatString
69 + "' does not ends with one of the following characters: "
70 + DESCRIPTORS);
71 }
72 _descriptorType = INT_DESCRIPTORS.indexOf(_descriptor) >= 0
73 ? INT_DESCRIPTOR : FLOAT_DESCRIPTOR;
74 if (formatString.length() > 1) {
75 switch (formatString.charAt(0)) {
76 case '-':
77 _flushLeft = true;
78 formatString = formatString.substring(1);
79 break;
80 case '0':
81 _leadingZeros = true;
82 formatString = formatString.substring(1);
83 break;
84 case '+':
85 _alwaysSign = true;
86 formatString = formatString.substring(1);
87 break;
88 }
89 len = formatString.length() - 1;
90 int index = formatString.indexOf('.');
91 _decimalPoint = index >= 0;
92 int last = _decimalPoint ? index : len;
93 if (last > 0) {
94 _width = Integer.parseInt(formatString.substring(0, last));
95 }
96 if (_decimalPoint) {
97 index++;
98 if (index < len) {
99 _precision = Integer.parseInt(formatString.substring(index, len));
100 }
101 }
102 }
103 _tenToPrecision = power(10, _precision);
104 }
105
106
112 public void form(StringBuffer buffer, long number) {
113 if (_descriptorType == FLOAT_DESCRIPTOR) {
114 form(buffer, (double) number);
115 } else {
116 buffer.append(form(number < 0,
118 Long.toString(Math.abs(number),
119 _descriptor == 'o' ? 8
120 : (_descriptor == 'x' ? 16 : 10)),
121 ""));
122 }
123 }
124
125
131 public void form(StringBuffer buffer, double number) {
132 if (_descriptorType == INT_DESCRIPTOR) {
133 form(buffer, (long) Math.floor(number + 0.5));
134 } else if (_descriptor == 'f') {
135 buffer.append(formF(number));
136 } else if (_descriptor == 'e' || _descriptor == 'E') {
137 buffer.append(formE(number));
138 } else if (_descriptor == 'g' || _descriptor == 'G') {
139 String formF = formF(number);
140 String formE = formE(number);
141 buffer.append(formF.length() > formE.length() ? formE : formF);
142 }
143 }
144
145 private String form(boolean negativeValue, String intPart, String fracPart) {
146 int len = intPart.length() + fracPart.length();
147
148 StringBuffer result = new StringBuffer ();
150 int count = 0;
151
152 if (_alwaysSign || negativeValue) {
154 result.append(negativeValue ? '-' : '+');
155 count++;
156 }
157
158 if (_leadingZeros) {
160 for (int i = count + len; i < _width; i++) {
161 result.append('0');
162 count++;
163 }
164 }
165
166 result.append(intPart).append(fracPart);
168 count += len;
169
170 if (_flushLeft) {
172 for (; count < _width; count++) {
173 result.append(' ');
174 }
175 } else {
176 for (; count < _width; count++) {
177 result.insert(0, ' ');
178 }
179 }
180
181 return new String (result);
182 }
183
184
185 private String formE(double number) {
186 int exponent = 0;
188 String zeros = "00000000000000000000000".substring(0, _precision + 1);
189 if (number != 0) {
190 exponent = (int) Math.floor(Math.log(Math.abs(number)) / Math.log(10));
191 double mantisse = Math.floor(Math.abs(number * power(10.0,
192 _precision - exponent)) + 0.5);
193 if (mantisse >= 10 * _tenToPrecision) {
194 exponent++;
195 mantisse = Math.floor(Math.abs(number * power(10.0,
196 _precision - exponent)) + 0.5);
197 }
198 zeros = Long.toString((long) mantisse);
199 }
200
201 StringBuffer fracPart = new StringBuffer ();
203 if (_decimalPoint) {
204 fracPart.append('.').append(zeros.substring(1));
205 }
206
207 fracPart.append(Character.isLowerCase(_descriptor) ? 'e': 'E')
209 .append(exponent < 0 ? '-' : '+');
210 exponent = Math.abs(exponent);
211 for (int i = 0, n = fracPart.length(); i < 3; i++) {
212 fracPart.insert(n, Character.forDigit(exponent % 10, 10));
213 exponent /= 10;
214 }
215
216 return form(number < 0, zeros.substring(0, 1), new String (fracPart));
217 }
218
219
220 private String formF(double number) {
221 double multiplier = number < 0 ? - _tenToPrecision : _tenToPrecision;
223 String digits
224 = Long.toString((long) Math.floor(number * multiplier + 0.5));
225 String intPart = digits;
226 StringBuffer fracPart = new StringBuffer ();
227 if (_decimalPoint) {
228 int len = digits.length() - _precision;
229 fracPart.append('.').append(digits.substring(Math.max(0, len)));
230 if (len > 0) {
231 intPart = digits.substring(0, len);
232 } else {
233 intPart = "0";
234 for (; len < 0; len++) {
235 fracPart.insert(1, '0');
236 }
237 }
238 }
239
240 return form(number < 0, intPart, new String (fracPart));
241 }
242 }
243 |
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