1 /*
2 * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import sun.misc.FloatingDecimal;
29 import sun.misc.FpUtils;
30 import sun.misc.FloatConsts;
31 import sun.misc.DoubleConsts;
32
33 /**
34 * The {@code Float} class wraps a value of primitive type
35 * {@code float} in an object. An object of type
36 * {@code Float} contains a single field whose type is
37 * {@code float}.
38 *
39 * <p>In addition, this class provides several methods for converting a
40 * {@code float} to a {@code String} and a
41 * {@code String} to a {@code float}, as well as other
42 * constants and methods useful when dealing with a
43 * {@code float}.
44 *
45 * @author Lee Boynton
46 * @author Arthur van Hoff
47 * @author Joseph D. Darcy
48 * @since JDK1.0
49 */
50 public final class Float extends Number implements Comparable<Float> {
51 /**
52 * A constant holding the positive infinity of type
53 * {@code float}. It is equal to the value returned by
54 * {@code Float.intBitsToFloat(0x7f800000)}.
55 */
56 public static final float POSITIVE_INFINITY = 1.0f / 0.0f;
57
58 /**
59 * A constant holding the negative infinity of type
60 * {@code float}. It is equal to the value returned by
61 * {@code Float.intBitsToFloat(0xff800000)}.
62 */
63 public static final float NEGATIVE_INFINITY = -1.0f / 0.0f;
64
65 /**
66 * A constant holding a Not-a-Number (NaN) value of type
67 * {@code float}. It is equivalent to the value returned by
68 * {@code Float.intBitsToFloat(0x7fc00000)}.
69 */
70 public static final float NaN = 0.0f / 0.0f;
71
72 /**
73 * A constant holding the largest positive finite value of type
74 * {@code float}, (2-2<sup>-23</sup>)·2<sup>127</sup>.
75 * It is equal to the hexadecimal floating-point literal
76 * {@code 0x1.fffffeP+127f} and also equal to
77 * {@code Float.intBitsToFloat(0x7f7fffff)}.
78 */
79 public static final float MAX_VALUE = 0x1.fffffeP+127f; // 3.4028235e+38f
80
81 /**
82 * A constant holding the smallest positive normal value of type
83 * {@code float}, 2<sup>-126</sup>. It is equal to the
84 * hexadecimal floating-point literal {@code 0x1.0p-126f} and also
85 * equal to {@code Float.intBitsToFloat(0x00800000)}.
86 *
87 * @since 1.6
88 */
89 public static final float MIN_NORMAL = 0x1.0p-126f; // 1.17549435E-38f
90
91 /**
92 * A constant holding the smallest positive nonzero value of type
93 * {@code float}, 2<sup>-149</sup>. It is equal to the
94 * hexadecimal floating-point literal {@code 0x0.000002P-126f}
95 * and also equal to {@code Float.intBitsToFloat(0x1)}.
96 */
97 public static final float MIN_VALUE = 0x0.000002P-126f; // 1.4e-45f
98
99 /**
100 * Maximum exponent a finite {@code float} variable may have. It
101 * is equal to the value returned by {@code
102 * Math.getExponent(Float.MAX_VALUE)}.
103 *
104 * @since 1.6
105 */
106 public static final int MAX_EXPONENT = 127;
107
108 /**
109 * Minimum exponent a normalized {@code float} variable may have.
110 * It is equal to the value returned by {@code
111 * Math.getExponent(Float.MIN_NORMAL)}.
112 *
113 * @since 1.6
114 */
115 public static final int MIN_EXPONENT = -126;
116
117 /**
118 * The number of bits used to represent a {@code float} value.
119 *
120 * @since 1.5
121 */
122 public static final int SIZE = 32;
123
124 /**
125 * The {@code Class} instance representing the primitive type
126 * {@code float}.
127 *
128 * @since JDK1.1
129 */
130 public static final Class<Float> TYPE = Class.getPrimitiveClass("float");
131
132 /**
133 * Returns a string representation of the {@code float}
134 * argument. All characters mentioned below are ASCII characters.
135 * <ul>
136 * <li>If the argument is NaN, the result is the string
137 * "{@code NaN}".
138 * <li>Otherwise, the result is a string that represents the sign and
139 * magnitude (absolute value) of the argument. If the sign is
140 * negative, the first character of the result is
141 * '{@code -}' (<code>'\u002D'</code>); if the sign is
142 * positive, no sign character appears in the result. As for
143 * the magnitude <i>m</i>:
144 * <ul>
145 * <li>If <i>m</i> is infinity, it is represented by the characters
146 * {@code "Infinity"}; thus, positive infinity produces
147 * the result {@code "Infinity"} and negative infinity
148 * produces the result {@code "-Infinity"}.
149 * <li>If <i>m</i> is zero, it is represented by the characters
150 * {@code "0.0"}; thus, negative zero produces the result
151 * {@code "-0.0"} and positive zero produces the result
152 * {@code "0.0"}.
153 * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but
154 * less than 10<sup>7</sup>, then it is represented as the
155 * integer part of <i>m</i>, in decimal form with no leading
156 * zeroes, followed by '{@code .}'
157 * (<code>'\u002E'</code>), followed by one or more
158 * decimal digits representing the fractional part of
159 * <i>m</i>.
160 * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or
161 * equal to 10<sup>7</sup>, then it is represented in
162 * so-called "computerized scientific notation." Let <i>n</i>
163 * be the unique integer such that 10<sup><i>n</i> </sup>≤
164 * <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i>
165 * be the mathematically exact quotient of <i>m</i> and
166 * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10.
167 * The magnitude is then represented as the integer part of
168 * <i>a</i>, as a single decimal digit, followed by
169 * '{@code .}' (<code>'\u002E'</code>), followed by
170 * decimal digits representing the fractional part of
171 * <i>a</i>, followed by the letter '{@code E}'
172 * (<code>'\u0045'</code>), followed by a representation
173 * of <i>n</i> as a decimal integer, as produced by the
174 * method {@link java.lang.Integer#toString(int)}.
175 *
176 * </ul>
177 * </ul>
178 * How many digits must be printed for the fractional part of
179 * <i>m</i> or <i>a</i>? There must be at least one digit
180 * to represent the fractional part, and beyond that as many, but
181 * only as many, more digits as are needed to uniquely distinguish
182 * the argument value from adjacent values of type
183 * {@code float}. That is, suppose that <i>x</i> is the
184 * exact mathematical value represented by the decimal
185 * representation produced by this method for a finite nonzero
186 * argument <i>f</i>. Then <i>f</i> must be the {@code float}
187 * value nearest to <i>x</i>; or, if two {@code float} values are
188 * equally close to <i>x</i>, then <i>f</i> must be one of
189 * them and the least significant bit of the significand of
190 * <i>f</i> must be {@code 0}.
191 *
192 * <p>To create localized string representations of a floating-point
193 * value, use subclasses of {@link java.text.NumberFormat}.
194 *
195 * @param f the float to be converted.
196 * @return a string representation of the argument.
197 */
198 public static String toString(float f) {
199 return new FloatingDecimal(f).toJavaFormatString();
200 }
201
202 /**
203 * Returns a hexadecimal string representation of the
204 * {@code float} argument. All characters mentioned below are
205 * ASCII characters.
206 *
207 * <ul>
208 * <li>If the argument is NaN, the result is the string
209 * "{@code NaN}".
210 * <li>Otherwise, the result is a string that represents the sign and
211 * magnitude (absolute value) of the argument. If the sign is negative,
212 * the first character of the result is '{@code -}'
213 * (<code>'\u002D'</code>); if the sign is positive, no sign character
214 * appears in the result. As for the magnitude <i>m</i>:
215 *
216 * <ul>
217 * <li>If <i>m</i> is infinity, it is represented by the string
218 * {@code "Infinity"}; thus, positive infinity produces the
219 * result {@code "Infinity"} and negative infinity produces
220 * the result {@code "-Infinity"}.
221 *
222 * <li>If <i>m</i> is zero, it is represented by the string
223 * {@code "0x0.0p0"}; thus, negative zero produces the result
224 * {@code "-0x0.0p0"} and positive zero produces the result
225 * {@code "0x0.0p0"}.
226 *
227 * <li>If <i>m</i> is a {@code float} value with a
228 * normalized representation, substrings are used to represent the
229 * significand and exponent fields. The significand is
230 * represented by the characters {@code "0x1."}
231 * followed by a lowercase hexadecimal representation of the rest
232 * of the significand as a fraction. Trailing zeros in the
233 * hexadecimal representation are removed unless all the digits
234 * are zero, in which case a single zero is used. Next, the
235 * exponent is represented by {@code "p"} followed
236 * by a decimal string of the unbiased exponent as if produced by
237 * a call to {@link Integer#toString(int) Integer.toString} on the
238 * exponent value.
239 *
240 * <li>If <i>m</i> is a {@code float} value with a subnormal
241 * representation, the significand is represented by the
242 * characters {@code "0x0."} followed by a
243 * hexadecimal representation of the rest of the significand as a
244 * fraction. Trailing zeros in the hexadecimal representation are
245 * removed. Next, the exponent is represented by
246 * {@code "p-126"}. Note that there must be at
247 * least one nonzero digit in a subnormal significand.
248 *
249 * </ul>
250 *
251 * </ul>
252 *
253 * <table border>
254 * <caption><h3>Examples</h3></caption>
255 * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
256 * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
257 * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td>
258 * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
259 * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
260 * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
261 * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td>
262 * <tr><td>{@code Float.MAX_VALUE}</td>
263 * <td>{@code 0x1.fffffep127}</td>
264 * <tr><td>{@code Minimum Normal Value}</td>
265 * <td>{@code 0x1.0p-126}</td>
266 * <tr><td>{@code Maximum Subnormal Value}</td>
267 * <td>{@code 0x0.fffffep-126}</td>
268 * <tr><td>{@code Float.MIN_VALUE}</td>
269 * <td>{@code 0x0.000002p-126}</td>
270 * </table>
271 * @param f the {@code float} to be converted.
272 * @return a hex string representation of the argument.
273 * @since 1.5
274 * @author Joseph D. Darcy
275 */
276 public static String toHexString(float f) {
277 if (Math.abs(f) < FloatConsts.MIN_NORMAL
278 && f != 0.0f ) {// float subnormal
279 // Adjust exponent to create subnormal double, then
280 // replace subnormal double exponent with subnormal float
281 // exponent
282 String s = Double.toHexString(FpUtils.scalb((double)f,
283 /* -1022+126 */
284 DoubleConsts.MIN_EXPONENT-
285 FloatConsts.MIN_EXPONENT));
286 return s.replaceFirst("p-1022$", "p-126");
287 }
288 else // double string will be the same as float string
289 return Double.toHexString(f);
290 }
291
292 /**
293 * Returns a {@code Float} object holding the
294 * {@code float} value represented by the argument string
295 * {@code s}.
296 *
297 * <p>If {@code s} is {@code null}, then a
298 * {@code NullPointerException} is thrown.
299 *
300 * <p>Leading and trailing whitespace characters in {@code s}
301 * are ignored. Whitespace is removed as if by the {@link
302 * String#trim} method; that is, both ASCII space and control
303 * characters are removed. The rest of {@code s} should
304 * constitute a <i>FloatValue</i> as described by the lexical
305 * syntax rules:
306 *
307 * <blockquote>
308 * <dl>
309 * <dt><i>FloatValue:</i>
310 * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
311 * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
312 * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
313 * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
314 * <dd><i>SignedInteger</i>
315 * </dl>
316 *
317 * <p>
318 *
319 * <dl>
320 * <dt><i>HexFloatingPointLiteral</i>:
321 * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
322 * </dl>
323 *
324 * <p>
325 *
326 * <dl>
327 * <dt><i>HexSignificand:</i>
328 * <dd><i>HexNumeral</i>
329 * <dd><i>HexNumeral</i> {@code .}
330 * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
331 * </i>{@code .}<i> HexDigits</i>
332 * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
333 * </i>{@code .} <i>HexDigits</i>
334 * </dl>
335 *
336 * <p>
337 *
338 * <dl>
339 * <dt><i>BinaryExponent:</i>
340 * <dd><i>BinaryExponentIndicator SignedInteger</i>
341 * </dl>
342 *
343 * <p>
344 *
345 * <dl>
346 * <dt><i>BinaryExponentIndicator:</i>
347 * <dd>{@code p}
348 * <dd>{@code P}
349 * </dl>
350 *
351 * </blockquote>
352 *
353 * where <i>Sign</i>, <i>FloatingPointLiteral</i>,
354 * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and
355 * <i>FloatTypeSuffix</i> are as defined in the lexical structure
356 * sections of
357 * <cite>The Java™ Language Specification</cite>,
358 * except that underscores are not accepted between digits.
359 * If {@code s} does not have the form of
360 * a <i>FloatValue</i>, then a {@code NumberFormatException}
361 * is thrown. Otherwise, {@code s} is regarded as
362 * representing an exact decimal value in the usual
363 * "computerized scientific notation" or as an exact
364 * hexadecimal value; this exact numerical value is then
365 * conceptually converted to an "infinitely precise"
366 * binary value that is then rounded to type {@code float}
367 * by the usual round-to-nearest rule of IEEE 754 floating-point
368 * arithmetic, which includes preserving the sign of a zero
369 * value.
370 *
371 * Note that the round-to-nearest rule also implies overflow and
372 * underflow behaviour; if the exact value of {@code s} is large
373 * enough in magnitude (greater than or equal to ({@link
374 * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2),
375 * rounding to {@code float} will result in an infinity and if the
376 * exact value of {@code s} is small enough in magnitude (less
377 * than or equal to {@link #MIN_VALUE}/2), rounding to float will
378 * result in a zero.
379 *
380 * Finally, after rounding a {@code Float} object representing
381 * this {@code float} value is returned.
382 *
383 * <p>To interpret localized string representations of a
384 * floating-point value, use subclasses of {@link
385 * java.text.NumberFormat}.
386 *
387 * <p>Note that trailing format specifiers, specifiers that
388 * determine the type of a floating-point literal
389 * ({@code 1.0f} is a {@code float} value;
390 * {@code 1.0d} is a {@code double} value), do
391 * <em>not</em> influence the results of this method. In other
392 * words, the numerical value of the input string is converted
393 * directly to the target floating-point type. In general, the
394 * two-step sequence of conversions, string to {@code double}
395 * followed by {@code double} to {@code float}, is
396 * <em>not</em> equivalent to converting a string directly to
397 * {@code float}. For example, if first converted to an
398 * intermediate {@code double} and then to
399 * {@code float}, the string<br>
400 * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br>
401 * results in the {@code float} value
402 * {@code 1.0000002f}; if the string is converted directly to
403 * {@code float}, <code>1.000000<b>1</b>f</code> results.
404 *
405 * <p>To avoid calling this method on an invalid string and having
406 * a {@code NumberFormatException} be thrown, the documentation
407 * for {@link Double#valueOf Double.valueOf} lists a regular
408 * expression which can be used to screen the input.
409 *
410 * @param s the string to be parsed.
411 * @return a {@code Float} object holding the value
412 * represented by the {@code String} argument.
413 * @throws NumberFormatException if the string does not contain a
414 * parsable number.
415 */
416 public static Float valueOf(String s) throws NumberFormatException {
417 return new Float(FloatingDecimal.readJavaFormatString(s).floatValue());
418 }
419
420 /**
421 * Returns a {@code Float} instance representing the specified
422 * {@code float} value.
423 * If a new {@code Float} instance is not required, this method
424 * should generally be used in preference to the constructor
425 * {@link #Float(float)}, as this method is likely to yield
426 * significantly better space and time performance by caching
427 * frequently requested values.
428 *
429 * @param f a float value.
430 * @return a {@code Float} instance representing {@code f}.
431 * @since 1.5
432 */
433 public static Float valueOf(float f) {
434 return new Float(f);
435 }
436
437 /**
438 * Returns a new {@code float} initialized to the value
439 * represented by the specified {@code String}, as performed
440 * by the {@code valueOf} method of class {@code Float}.
441 *
442 * @param s the string to be parsed.
443 * @return the {@code float} value represented by the string
444 * argument.
445 * @throws NullPointerException if the string is null
446 * @throws NumberFormatException if the string does not contain a
447 * parsable {@code float}.
448 * @see java.lang.Float#valueOf(String)
449 * @since 1.2
450 */
451 public static float parseFloat(String s) throws NumberFormatException {
452 return FloatingDecimal.readJavaFormatString(s).floatValue();
453 }
454
455 /**
456 * Returns {@code true} if the specified number is a
457 * Not-a-Number (NaN) value, {@code false} otherwise.
458 *
459 * @param v the value to be tested.
460 * @return {@code true} if the argument is NaN;
461 * {@code false} otherwise.
462 */
463 static public boolean isNaN(float v) {
464 return (v != v);
465 }
466
467 /**
468 * Returns {@code true} if the specified number is infinitely
469 * large in magnitude, {@code false} otherwise.
470 *
471 * @param v the value to be tested.
472 * @return {@code true} if the argument is positive infinity or
473 * negative infinity; {@code false} otherwise.
474 */
475 static public boolean isInfinite(float v) {
476 return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
477 }
478
479 /**
480 * The value of the Float.
481 *
482 * @serial
483 */
484 private final float value;
485
486 /**
487 * Constructs a newly allocated {@code Float} object that
488 * represents the primitive {@code float} argument.
489 *
490 * @param value the value to be represented by the {@code Float}.
491 */
492 public Float(float value) {
493 this.value = value;
494 }
495
496 /**
497 * Constructs a newly allocated {@code Float} object that
498 * represents the argument converted to type {@code float}.
499 *
500 * @param value the value to be represented by the {@code Float}.
501 */
502 public Float(double value) {
503 this.value = (float)value;
504 }
505
506 /**
507 * Constructs a newly allocated {@code Float} object that
508 * represents the floating-point value of type {@code float}
509 * represented by the string. The string is converted to a
510 * {@code float} value as if by the {@code valueOf} method.
511 *
512 * @param s a string to be converted to a {@code Float}.
513 * @throws NumberFormatException if the string does not contain a
514 * parsable number.
515 * @see java.lang.Float#valueOf(java.lang.String)
516 */
517 public Float(String s) throws NumberFormatException {
518 // REMIND: this is inefficient
519 this(valueOf(s).floatValue());
520 }
521
522 /**
523 * Returns {@code true} if this {@code Float} value is a
524 * Not-a-Number (NaN), {@code false} otherwise.
525 *
526 * @return {@code true} if the value represented by this object is
527 * NaN; {@code false} otherwise.
528 */
529 public boolean isNaN() {
530 return isNaN(value);
531 }
532
533 /**
534 * Returns {@code true} if this {@code Float} value is
535 * infinitely large in magnitude, {@code false} otherwise.
536 *
537 * @return {@code true} if the value represented by this object is
538 * positive infinity or negative infinity;
539 * {@code false} otherwise.
540 */
541 public boolean isInfinite() {
542 return isInfinite(value);
543 }
544
545 /**
546 * Returns a string representation of this {@code Float} object.
547 * The primitive {@code float} value represented by this object
548 * is converted to a {@code String} exactly as if by the method
549 * {@code toString} of one argument.
550 *
551 * @return a {@code String} representation of this object.
552 * @see java.lang.Float#toString(float)
553 */
554 public String toString() {
555 return Float.toString(value);
556 }
557
558 /**
559 * Returns the value of this {@code Float} as a {@code byte} (by
560 * casting to a {@code byte}).
561 *
562 * @return the {@code float} value represented by this object
563 * converted to type {@code byte}
564 */
565 public byte byteValue() {
566 return (byte)value;
567 }
568
569 /**
570 * Returns the value of this {@code Float} as a {@code short} (by
571 * casting to a {@code short}).
572 *
573 * @return the {@code float} value represented by this object
574 * converted to type {@code short}
575 * @since JDK1.1
576 */
577 public short shortValue() {
578 return (short)value;
579 }
580
581 /**
582 * Returns the value of this {@code Float} as an {@code int} (by
583 * casting to type {@code int}).
584 *
585 * @return the {@code float} value represented by this object
586 * converted to type {@code int}
587 */
588 public int intValue() {
589 return (int)value;
590 }
591
592 /**
593 * Returns value of this {@code Float} as a {@code long} (by
594 * casting to type {@code long}).
595 *
596 * @return the {@code float} value represented by this object
597 * converted to type {@code long}
598 */
599 public long longValue() {
600 return (long)value;
601 }
602
603 /**
604 * Returns the {@code float} value of this {@code Float} object.
605 *
606 * @return the {@code float} value represented by this object
607 */
608 public float floatValue() {
609 return value;
610 }
611
612 /**
613 * Returns the {@code double} value of this {@code Float} object.
614 *
615 * @return the {@code float} value represented by this
616 * object is converted to type {@code double} and the
617 * result of the conversion is returned.
618 */
619 public double doubleValue() {
620 return (double)value;
621 }
622
623 /**
624 * Returns a hash code for this {@code Float} object. The
625 * result is the integer bit representation, exactly as produced
626 * by the method {@link #floatToIntBits(float)}, of the primitive
627 * {@code float} value represented by this {@code Float}
628 * object.
629 *
630 * @return a hash code value for this object.
631 */
632 public int hashCode() {
633 return floatToIntBits(value);
634 }
635
636 /**
637
638 * Compares this object against the specified object. The result
639 * is {@code true} if and only if the argument is not
640 * {@code null} and is a {@code Float} object that
641 * represents a {@code float} with the same value as the
642 * {@code float} represented by this object. For this
643 * purpose, two {@code float} values are considered to be the
644 * same if and only if the method {@link #floatToIntBits(float)}
645 * returns the identical {@code int} value when applied to
646 * each.
647 *
648 * <p>Note that in most cases, for two instances of class
649 * {@code Float}, {@code f1} and {@code f2}, the value
650 * of {@code f1.equals(f2)} is {@code true} if and only if
651 *
652 * <blockquote><pre>
653 * f1.floatValue() == f2.floatValue()
654 * </pre></blockquote>
655 *
656 * <p>also has the value {@code true}. However, there are two exceptions:
657 * <ul>
658 * <li>If {@code f1} and {@code f2} both represent
659 * {@code Float.NaN}, then the {@code equals} method returns
660 * {@code true}, even though {@code Float.NaN==Float.NaN}
661 * has the value {@code false}.
662 * <li>If {@code f1} represents {@code +0.0f} while
663 * {@code f2} represents {@code -0.0f}, or vice
664 * versa, the {@code equal} test has the value
665 * {@code false}, even though {@code 0.0f==-0.0f}
666 * has the value {@code true}.
667 * </ul>
668 *
669 * This definition allows hash tables to operate properly.
670 *
671 * @param obj the object to be compared
672 * @return {@code true} if the objects are the same;
673 * {@code false} otherwise.
674 * @see java.lang.Float#floatToIntBits(float)
675 */
676 public boolean equals(Object obj) {
677 return (obj instanceof Float)
678 && (floatToIntBits(((Float)obj).value) == floatToIntBits(value));
679 }
680
681 /**
682 * Returns a representation of the specified floating-point value
683 * according to the IEEE 754 floating-point "single format" bit
684 * layout.
685 *
686 * <p>Bit 31 (the bit that is selected by the mask
687 * {@code 0x80000000}) represents the sign of the floating-point
688 * number.
689 * Bits 30-23 (the bits that are selected by the mask
690 * {@code 0x7f800000}) represent the exponent.
691 * Bits 22-0 (the bits that are selected by the mask
692 * {@code 0x007fffff}) represent the significand (sometimes called
693 * the mantissa) of the floating-point number.
694 *
695 * <p>If the argument is positive infinity, the result is
696 * {@code 0x7f800000}.
697 *
698 * <p>If the argument is negative infinity, the result is
699 * {@code 0xff800000}.
700 *
701 * <p>If the argument is NaN, the result is {@code 0x7fc00000}.
702 *
703 * <p>In all cases, the result is an integer that, when given to the
704 * {@link #intBitsToFloat(int)} method, will produce a floating-point
705 * value the same as the argument to {@code floatToIntBits}
706 * (except all NaN values are collapsed to a single
707 * "canonical" NaN value).
708 *
709 * @param value a floating-point number.
710 * @return the bits that represent the floating-point number.
711 */
712 public static int floatToIntBits(float value) {
713 int result = floatToRawIntBits(value);
714 // Check for NaN based on values of bit fields, maximum
715 // exponent and nonzero significand.
716 if ( ((result & FloatConsts.EXP_BIT_MASK) ==
717 FloatConsts.EXP_BIT_MASK) &&
718 (result & FloatConsts.SIGNIF_BIT_MASK) != 0)
719 result = 0x7fc00000;
720 return result;
721 }
722
723 /**
724 * Returns a representation of the specified floating-point value
725 * according to the IEEE 754 floating-point "single format" bit
726 * layout, preserving Not-a-Number (NaN) values.
727 *
728 * <p>Bit 31 (the bit that is selected by the mask
729 * {@code 0x80000000}) represents the sign of the floating-point
730 * number.
731 * Bits 30-23 (the bits that are selected by the mask
732 * {@code 0x7f800000}) represent the exponent.
733 * Bits 22-0 (the bits that are selected by the mask
734 * {@code 0x007fffff}) represent the significand (sometimes called
735 * the mantissa) of the floating-point number.
736 *
737 * <p>If the argument is positive infinity, the result is
738 * {@code 0x7f800000}.
739 *
740 * <p>If the argument is negative infinity, the result is
741 * {@code 0xff800000}.
742 *
743 * <p>If the argument is NaN, the result is the integer representing
744 * the actual NaN value. Unlike the {@code floatToIntBits}
745 * method, {@code floatToRawIntBits} does not collapse all the
746 * bit patterns encoding a NaN to a single "canonical"
747 * NaN value.
748 *
749 * <p>In all cases, the result is an integer that, when given to the
750 * {@link #intBitsToFloat(int)} method, will produce a
751 * floating-point value the same as the argument to
752 * {@code floatToRawIntBits}.
753 *
754 * @param value a floating-point number.
755 * @return the bits that represent the floating-point number.
756 * @since 1.3
757 */
758 public static native int floatToRawIntBits(float value);
759
760 /**
761 * Returns the {@code float} value corresponding to a given
762 * bit representation.
763 * The argument is considered to be a representation of a
764 * floating-point value according to the IEEE 754 floating-point
765 * "single format" bit layout.
766 *
767 * <p>If the argument is {@code 0x7f800000}, the result is positive
768 * infinity.
769 *
770 * <p>If the argument is {@code 0xff800000}, the result is negative
771 * infinity.
772 *
773 * <p>If the argument is any value in the range
774 * {@code 0x7f800001} through {@code 0x7fffffff} or in
775 * the range {@code 0xff800001} through
776 * {@code 0xffffffff}, the result is a NaN. No IEEE 754
777 * floating-point operation provided by Java can distinguish
778 * between two NaN values of the same type with different bit
779 * patterns. Distinct values of NaN are only distinguishable by
780 * use of the {@code Float.floatToRawIntBits} method.
781 *
782 * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
783 * values that can be computed from the argument:
784 *
785 * <blockquote><pre>
786 * int s = ((bits >> 31) == 0) ? 1 : -1;
787 * int e = ((bits >> 23) & 0xff);
788 * int m = (e == 0) ?
789 * (bits & 0x7fffff) << 1 :
790 * (bits & 0x7fffff) | 0x800000;
791 * </pre></blockquote>
792 *
793 * Then the floating-point result equals the value of the mathematical
794 * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>.
795 *
796 * <p>Note that this method may not be able to return a
797 * {@code float} NaN with exactly same bit pattern as the
798 * {@code int} argument. IEEE 754 distinguishes between two
799 * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The
800 * differences between the two kinds of NaN are generally not
801 * visible in Java. Arithmetic operations on signaling NaNs turn
802 * them into quiet NaNs with a different, but often similar, bit
803 * pattern. However, on some processors merely copying a
804 * signaling NaN also performs that conversion. In particular,
805 * copying a signaling NaN to return it to the calling method may
806 * perform this conversion. So {@code intBitsToFloat} may
807 * not be able to return a {@code float} with a signaling NaN
808 * bit pattern. Consequently, for some {@code int} values,
809 * {@code floatToRawIntBits(intBitsToFloat(start))} may
810 * <i>not</i> equal {@code start}. Moreover, which
811 * particular bit patterns represent signaling NaNs is platform
812 * dependent; although all NaN bit patterns, quiet or signaling,
813 * must be in the NaN range identified above.
814 *
815 * @param bits an integer.
816 * @return the {@code float} floating-point value with the same bit
817 * pattern.
818 */
819 public static native float intBitsToFloat(int bits);
820
821 /**
822 * Compares two {@code Float} objects numerically. There are
823 * two ways in which comparisons performed by this method differ
824 * from those performed by the Java language numerical comparison
825 * operators ({@code <, <=, ==, >=, >}) when
826 * applied to primitive {@code float} values:
827 *
828 * <ul><li>
829 * {@code Float.NaN} is considered by this method to
830 * be equal to itself and greater than all other
831 * {@code float} values
832 * (including {@code Float.POSITIVE_INFINITY}).
833 * <li>
834 * {@code 0.0f} is considered by this method to be greater
835 * than {@code -0.0f}.
836 * </ul>
837 *
838 * This ensures that the <i>natural ordering</i> of {@code Float}
839 * objects imposed by this method is <i>consistent with equals</i>.
840 *
841 * @param anotherFloat the {@code Float} to be compared.
842 * @return the value {@code 0} if {@code anotherFloat} is
843 * numerically equal to this {@code Float}; a value
844 * less than {@code 0} if this {@code Float}
845 * is numerically less than {@code anotherFloat};
846 * and a value greater than {@code 0} if this
847 * {@code Float} is numerically greater than
848 * {@code anotherFloat}.
849 *
850 * @since 1.2
851 * @see Comparable#compareTo(Object)
852 */
853 public int compareTo(Float anotherFloat) {
854 return Float.compare(value, anotherFloat.value);
855 }
856
857 /**
858 * Compares the two specified {@code float} values. The sign
859 * of the integer value returned is the same as that of the
860 * integer that would be returned by the call:
861 * <pre>
862 * new Float(f1).compareTo(new Float(f2))
863 * </pre>
864 *
865 * @param f1 the first {@code float} to compare.
866 * @param f2 the second {@code float} to compare.
867 * @return the value {@code 0} if {@code f1} is
868 * numerically equal to {@code f2}; a value less than
869 * {@code 0} if {@code f1} is numerically less than
870 * {@code f2}; and a value greater than {@code 0}
871 * if {@code f1} is numerically greater than
872 * {@code f2}.
873 * @since 1.4
874 */
875 public static int compare(float f1, float f2) {
876 if (f1 < f2)
877 return -1; // Neither val is NaN, thisVal is smaller
878 if (f1 > f2)
879 return 1; // Neither val is NaN, thisVal is larger
880
881 // Cannot use floatToRawIntBits because of possibility of NaNs.
882 int thisBits = Float.floatToIntBits(f1);
883 int anotherBits = Float.floatToIntBits(f2);
884
885 return (thisBits == anotherBits ? 0 : // Values are equal
886 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
887 1)); // (0.0, -0.0) or (NaN, !NaN)
888 }
889
890 /** use serialVersionUID from JDK 1.0.2 for interoperability */
891 private static final long serialVersionUID = -2671257302660747028L;
892 }