1 /*
2 * Copyright (c) 1994, 2011, 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.FloatConsts;
30 import sun.misc.DoubleConsts;
31
32 /**
33 * The {@code Float} class wraps a value of primitive type
34 * {@code float} in an object. An object of type
35 * {@code Float} contains a single field whose type is
36 * {@code float}.
37 *
38 * <p>In addition, this class provides several methods for converting a
39 * {@code float} to a {@code String} and a
40 * {@code String} to a {@code float}, as well as other
41 * constants and methods useful when dealing with a
42 * {@code float}.
43 *
44 * @author Lee Boynton
45 * @author Arthur van Hoff
46 * @author Joseph D. Darcy
47 * @since JDK1.0
48 */
49 public final class Float extends Number implements Comparable<Float> {
50 /**
51 * A constant holding the positive infinity of type
52 * {@code float}. It is equal to the value returned by
53 * {@code Float.intBitsToFloat(0x7f800000)}.
54 */
55 public static final float POSITIVE_INFINITY = 1.0f / 0.0f;
56
57 /**
58 * A constant holding the negative infinity of type
59 * {@code float}. It is equal to the value returned by
60 * {@code Float.intBitsToFloat(0xff800000)}.
61 */
62 public static final float NEGATIVE_INFINITY = -1.0f / 0.0f;
63
64 /**
65 * A constant holding a Not-a-Number (NaN) value of type
66 * {@code float}. It is equivalent to the value returned by
67 * {@code Float.intBitsToFloat(0x7fc00000)}.
68 */
69 public static final float NaN = 0.0f / 0.0f;
70
71 /**
72 * A constant holding the largest positive finite value of type
73 * {@code float}, (2-2<sup>-23</sup>)·2<sup>127</sup>.
74 * It is equal to the hexadecimal floating-point literal
75 * {@code 0x1.fffffeP+127f} and also equal to
76 * {@code Float.intBitsToFloat(0x7f7fffff)}.
77 */
78 public static final float MAX_VALUE = 0x1.fffffeP+127f; // 3.4028235e+38f
79
80 /**
81 * A constant holding the smallest positive normal value of type
82 * {@code float}, 2<sup>-126</sup>. It is equal to the
83 * hexadecimal floating-point literal {@code 0x1.0p-126f} and also
84 * equal to {@code Float.intBitsToFloat(0x00800000)}.
85 *
86 * @since 1.6
87 */
88 public static final float MIN_NORMAL = 0x1.0p-126f; // 1.17549435E-38f
89
90 /**
91 * A constant holding the smallest positive nonzero value of type
92 * {@code float}, 2<sup>-149</sup>. It is equal to the
93 * hexadecimal floating-point literal {@code 0x0.000002P-126f}
94 * and also equal to {@code Float.intBitsToFloat(0x1)}.
95 */
96 public static final float MIN_VALUE = 0x0.000002P-126f; // 1.4e-45f
97
98 /**
99 * Maximum exponent a finite {@code float} variable may have. It
100 * is equal to the value returned by {@code
101 * Math.getExponent(Float.MAX_VALUE)}.
102 *
103 * @since 1.6
104 */
105 public static final int MAX_EXPONENT = 127;
106
107 /**
108 * Minimum exponent a normalized {@code float} variable may have.
109 * It is equal to the value returned by {@code
110 * Math.getExponent(Float.MIN_NORMAL)}.
111 *
112 * @since 1.6
113 */
114 public static final int MIN_EXPONENT = -126;
115
116 /**
117 * The number of bits used to represent a {@code float} value.
118 *
119 * @since 1.5
120 */
121 public static final int SIZE = 32;
122
123 /**
124 * The {@code Class} instance representing the primitive type
125 * {@code float}.
126 *
127 * @since JDK1.1
128 */
129 public static final Class<Float> TYPE = Class.getPrimitiveClass("float");
130
131 /**
132 * Returns a string representation of the {@code float}
133 * argument. All characters mentioned below are ASCII characters.
134 * <ul>
135 * <li>If the argument is NaN, the result is the string
136 * "{@code NaN}".
137 * <li>Otherwise, the result is a string that represents the sign and
138 * magnitude (absolute value) of the argument. If the sign is
139 * negative, the first character of the result is
140 * '{@code -}' (<code>'\u002D'</code>); if the sign is
141 * positive, no sign character appears in the result. As for
142 * the magnitude <i>m</i>:
143 * <ul>
144 * <li>If <i>m</i> is infinity, it is represented by the characters
145 * {@code "Infinity"}; thus, positive infinity produces
146 * the result {@code "Infinity"} and negative infinity
147 * produces the result {@code "-Infinity"}.
148 * <li>If <i>m</i> is zero, it is represented by the characters
149 * {@code "0.0"}; thus, negative zero produces the result
150 * {@code "-0.0"} and positive zero produces the result
151 * {@code "0.0"}.
152 * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but
153 * less than 10<sup>7</sup>, then it is represented as the
154 * integer part of <i>m</i>, in decimal form with no leading
155 * zeroes, followed by '{@code .}'
156 * (<code>'\u002E'</code>), followed by one or more
157 * decimal digits representing the fractional part of
158 * <i>m</i>.
159 * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or
160 * equal to 10<sup>7</sup>, then it is represented in
161 * so-called "computerized scientific notation." Let <i>n</i>
162 * be the unique integer such that 10<sup><i>n</i> </sup>≤
163 * <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i>
164 * be the mathematically exact quotient of <i>m</i> and
165 * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10.
166 * The magnitude is then represented as the integer part of
167 * <i>a</i>, as a single decimal digit, followed by
168 * '{@code .}' (<code>'\u002E'</code>), followed by
169 * decimal digits representing the fractional part of
170 * <i>a</i>, followed by the letter '{@code E}'
171 * (<code>'\u0045'</code>), followed by a representation
172 * of <i>n</i> as a decimal integer, as produced by the
173 * method {@link java.lang.Integer#toString(int)}.
174 *
175 * </ul>
176 * </ul>
177 * How many digits must be printed for the fractional part of
178 * <i>m</i> or <i>a</i>? There must be at least one digit
179 * to represent the fractional part, and beyond that as many, but
180 * only as many, more digits as are needed to uniquely distinguish
181 * the argument value from adjacent values of type
182 * {@code float}. That is, suppose that <i>x</i> is the
183 * exact mathematical value represented by the decimal
184 * representation produced by this method for a finite nonzero
185 * argument <i>f</i>. Then <i>f</i> must be the {@code float}
186 * value nearest to <i>x</i>; or, if two {@code float} values are
187 * equally close to <i>x</i>, then <i>f</i> must be one of
188 * them and the least significant bit of the significand of
189 * <i>f</i> must be {@code 0}.
190 *
191 * <p>To create localized string representations of a floating-point
192 * value, use subclasses of {@link java.text.NumberFormat}.
193 *
194 * @param f the float to be converted.
195 * @return a string representation of the argument.
196 */
197 public static String toString(float f) {
198 return new FloatingDecimal(f).toJavaFormatString();
199 }
200
201 /**
202 * Returns a hexadecimal string representation of the
203 * {@code float} argument. All characters mentioned below are
204 * ASCII characters.
205 *
206 * <ul>
207 * <li>If the argument is NaN, the result is the string
208 * "{@code NaN}".
209 * <li>Otherwise, the result is a string that represents the sign and
210 * magnitude (absolute value) of the argument. If the sign is negative,
211 * the first character of the result is '{@code -}'
212 * (<code>'\u002D'</code>); if the sign is positive, no sign character
213 * appears in the result. As for the magnitude <i>m</i>:
214 *
215 * <ul>
216 * <li>If <i>m</i> is infinity, it is represented by the string
217 * {@code "Infinity"}; thus, positive infinity produces the
218 * result {@code "Infinity"} and negative infinity produces
219 * the result {@code "-Infinity"}.
220 *
221 * <li>If <i>m</i> is zero, it is represented by the string
222 * {@code "0x0.0p0"}; thus, negative zero produces the result
223 * {@code "-0x0.0p0"} and positive zero produces the result
224 * {@code "0x0.0p0"}.
225 *
226 * <li>If <i>m</i> is a {@code float} value with a
227 * normalized representation, substrings are used to represent the
228 * significand and exponent fields. The significand is
229 * represented by the characters {@code "0x1."}
230 * followed by a lowercase hexadecimal representation of the rest
231 * of the significand as a fraction. Trailing zeros in the
232 * hexadecimal representation are removed unless all the digits
233 * are zero, in which case a single zero is used. Next, the
234 * exponent is represented by {@code "p"} followed
235 * by a decimal string of the unbiased exponent as if produced by
236 * a call to {@link Integer#toString(int) Integer.toString} on the
237 * exponent value.
238 *
239 * <li>If <i>m</i> is a {@code float} value with a subnormal
240 * representation, the significand is represented by the
241 * characters {@code "0x0."} followed by a
242 * hexadecimal representation of the rest of the significand as a
243 * fraction. Trailing zeros in the hexadecimal representation are
244 * removed. Next, the exponent is represented by
245 * {@code "p-126"}. Note that there must be at
246 * least one nonzero digit in a subnormal significand.
247 *
248 * </ul>
249 *
250 * </ul>
251 *
252 * <table border>
253 * <caption><h3>Examples</h3></caption>
254 * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
255 * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
256 * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td>
257 * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
258 * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
259 * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
260 * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td>
261 * <tr><td>{@code Float.MAX_VALUE}</td>
262 * <td>{@code 0x1.fffffep127}</td>
263 * <tr><td>{@code Minimum Normal Value}</td>
264 * <td>{@code 0x1.0p-126}</td>
265 * <tr><td>{@code Maximum Subnormal Value}</td>
266 * <td>{@code 0x0.fffffep-126}</td>
267 * <tr><td>{@code Float.MIN_VALUE}</td>
268 * <td>{@code 0x0.000002p-126}</td>
269 * </table>
270 * @param f the {@code float} to be converted.
271 * @return a hex string representation of the argument.
272 * @since 1.5
273 * @author Joseph D. Darcy
274 */
275 public static String toHexString(float f) {
276 if (Math.abs(f) < FloatConsts.MIN_NORMAL
277 && f != 0.0f ) {// float subnormal
278 // Adjust exponent to create subnormal double, then
279 // replace subnormal double exponent with subnormal float
280 // exponent
281 String s = Double.toHexString(Math.scalb((double)f,
282 /* -1022+126 */
283 DoubleConsts.MIN_EXPONENT-
284 FloatConsts.MIN_EXPONENT));
285 return s.replaceFirst("p-1022$", "p-126");
286 }
287 else // double string will be the same as float string
288 return Double.toHexString(f);
289 }
290
291 /**
292 * Returns a {@code Float} object holding the
293 * {@code float} value represented by the argument string
294 * {@code s}.
295 *
296 * <p>If {@code s} is {@code null}, then a
297 * {@code NullPointerException} is thrown.
298 *
299 * <p>Leading and trailing whitespace characters in {@code s}
300 * are ignored. Whitespace is removed as if by the {@link
301 * String#trim} method; that is, both ASCII space and control
302 * characters are removed. The rest of {@code s} should
303 * constitute a <i>FloatValue</i> as described by the lexical
304 * syntax rules:
305 *
306 * <blockquote>
307 * <dl>
308 * <dt><i>FloatValue:</i>
309 * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
310 * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
311 * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
312 * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
313 * <dd><i>SignedInteger</i>
314 * </dl>
315 *
316 * <p>
317 *
318 * <dl>
319 * <dt><i>HexFloatingPointLiteral</i>:
320 * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
321 * </dl>
322 *
323 * <p>
324 *
325 * <dl>
326 * <dt><i>HexSignificand:</i>
327 * <dd><i>HexNumeral</i>
328 * <dd><i>HexNumeral</i> {@code .}
329 * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
330 * </i>{@code .}<i> HexDigits</i>
331 * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
332 * </i>{@code .} <i>HexDigits</i>
333 * </dl>
334 *
335 * <p>
336 *
337 * <dl>
338 * <dt><i>BinaryExponent:</i>
339 * <dd><i>BinaryExponentIndicator SignedInteger</i>
340 * </dl>
341 *
342 * <p>
343 *
344 * <dl>
345 * <dt><i>BinaryExponentIndicator:</i>
346 * <dd>{@code p}
347 * <dd>{@code P}
348 * </dl>
349 *
350 * </blockquote>
351 *
352 * where <i>Sign</i>, <i>FloatingPointLiteral</i>,
353 * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and
354 * <i>FloatTypeSuffix</i> are as defined in the lexical structure
355 * sections of
356 * <cite>The Java™ Language Specification</cite>,
357 * except that underscores are not accepted between digits.
358 * If {@code s} does not have the form of
359 * a <i>FloatValue</i>, then a {@code NumberFormatException}
360 * is thrown. Otherwise, {@code s} is regarded as
361 * representing an exact decimal value in the usual
362 * "computerized scientific notation" or as an exact
363 * hexadecimal value; this exact numerical value is then
364 * conceptually converted to an "infinitely precise"
365 * binary value that is then rounded to type {@code float}
366 * by the usual round-to-nearest rule of IEEE 754 floating-point
367 * arithmetic, which includes preserving the sign of a zero
368 * value.
369 *
370 * Note that the round-to-nearest rule also implies overflow and
371 * underflow behaviour; if the exact value of {@code s} is large
372 * enough in magnitude (greater than or equal to ({@link
373 * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2),
374 * rounding to {@code float} will result in an infinity and if the
375 * exact value of {@code s} is small enough in magnitude (less
376 * than or equal to {@link #MIN_VALUE}/2), rounding to float will
377 * result in a zero.
378 *
379 * Finally, after rounding a {@code Float} object representing
380 * this {@code float} value is returned.
381 *
382 * <p>To interpret localized string representations of a
383 * floating-point value, use subclasses of {@link
384 * java.text.NumberFormat}.
385 *
386 * <p>Note that trailing format specifiers, specifiers that
387 * determine the type of a floating-point literal
388 * ({@code 1.0f} is a {@code float} value;
389 * {@code 1.0d} is a {@code double} value), do
390 * <em>not</em> influence the results of this method. In other
391 * words, the numerical value of the input string is converted
392 * directly to the target floating-point type. In general, the
393 * two-step sequence of conversions, string to {@code double}
394 * followed by {@code double} to {@code float}, is
395 * <em>not</em> equivalent to converting a string directly to
396 * {@code float}. For example, if first converted to an
397 * intermediate {@code double} and then to
398 * {@code float}, the string<br>
399 * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br>
400 * results in the {@code float} value
401 * {@code 1.0000002f}; if the string is converted directly to
402 * {@code float}, <code>1.000000<b>1</b>f</code> results.
403 *
404 * <p>To avoid calling this method on an invalid string and having
405 * a {@code NumberFormatException} be thrown, the documentation
406 * for {@link Double#valueOf Double.valueOf} lists a regular
407 * expression which can be used to screen the input.
408 *
409 * @param s the string to be parsed.
410 * @return a {@code Float} object holding the value
411 * represented by the {@code String} argument.
412 * @throws NumberFormatException if the string does not contain a
413 * parsable number.
414 */
415 public static Float valueOf(String s) throws NumberFormatException {
416 return new Float(FloatingDecimal.readJavaFormatString(s).floatValue());
417 }
418
419 /**
420 * Returns a {@code Float} instance representing the specified
421 * {@code float} value.
422 * If a new {@code Float} instance is not required, this method
423 * should generally be used in preference to the constructor
424 * {@link #Float(float)}, as this method is likely to yield
425 * significantly better space and time performance by caching
426 * frequently requested values.
427 *
428 * @param f a float value.
429 * @return a {@code Float} instance representing {@code f}.
430 * @since 1.5
431 */
432 public static Float valueOf(float f) {
433 return new Float(f);
434 }
435
436 /**
437 * Returns a new {@code float} initialized to the value
438 * represented by the specified {@code String}, as performed
439 * by the {@code valueOf} method of class {@code Float}.
440 *
441 * @param s the string to be parsed.
442 * @return the {@code float} value represented by the string
443 * argument.
444 * @throws NullPointerException if the string is null
445 * @throws NumberFormatException if the string does not contain a
446 * parsable {@code float}.
447 * @see java.lang.Float#valueOf(String)
448 * @since 1.2
449 */
450 public static float parseFloat(String s) throws NumberFormatException {
451 return FloatingDecimal.readJavaFormatString(s).floatValue();
452 }
453
454 /**
455 * Returns {@code true} if the specified number is a
456 * Not-a-Number (NaN) value, {@code false} otherwise.
457 *
458 * @param v the value to be tested.
459 * @return {@code true} if the argument is NaN;
460 * {@code false} otherwise.
461 */
462 public static boolean isNaN(float v) {
463 return (v != v);
464 }
465
466 /**
467 * Returns {@code true} if the specified number is infinitely
468 * large in magnitude, {@code false} otherwise.
469 *
470 * @param v the value to be tested.
471 * @return {@code true} if the argument is positive infinity or
472 * negative infinity; {@code false} otherwise.
473 */
474 public static boolean isInfinite(float v) {
475 return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
476 }
477
478
479 /**
480 * Returns {@code true} if the argument is a finite floating-point
481 * value; returns {@code false} otherwise (for NaN and infinity
482 * arguments).
483 *
484 * @param f the {@code float} value to be tested
485 * @return {@code true} if the argument is a finite
486 * floating-point value, {@code false} otherwise.
487 * @since 1.8
488 */
489 public static boolean isFinite(float f) {
490 return Math.abs(f) <= FloatConsts.MAX_VALUE;
491 }
492
493 /**
494 * The value of the Float.
495 *
496 * @serial
497 */
498 private final float value;
499
500 /**
501 * Constructs a newly allocated {@code Float} object that
502 * represents the primitive {@code float} argument.
503 *
504 * @param value the value to be represented by the {@code Float}.
505 */
506 public Float(float value) {
507 this.value = value;
508 }
509
510 /**
511 * Constructs a newly allocated {@code Float} object that
512 * represents the argument converted to type {@code float}.
513 *
514 * @param value the value to be represented by the {@code Float}.
515 */
516 public Float(double value) {
517 this.value = (float)value;
518 }
519
520 /**
521 * Constructs a newly allocated {@code Float} object that
522 * represents the floating-point value of type {@code float}
523 * represented by the string. The string is converted to a
524 * {@code float} value as if by the {@code valueOf} method.
525 *
526 * @param s a string to be converted to a {@code Float}.
527 * @throws NumberFormatException if the string does not contain a
528 * parsable number.
529 * @see java.lang.Float#valueOf(java.lang.String)
530 */
531 public Float(String s) throws NumberFormatException {
532 // REMIND: this is inefficient
533 this(valueOf(s).floatValue());
534 }
535
536 /**
537 * Returns {@code true} if this {@code Float} value is a
538 * Not-a-Number (NaN), {@code false} otherwise.
539 *
540 * @return {@code true} if the value represented by this object is
541 * NaN; {@code false} otherwise.
542 */
543 public boolean isNaN() {
544 return isNaN(value);
545 }
546
547 /**
548 * Returns {@code true} if this {@code Float} value is
549 * infinitely large in magnitude, {@code false} otherwise.
550 *
551 * @return {@code true} if the value represented by this object is
552 * positive infinity or negative infinity;
553 * {@code false} otherwise.
554 */
555 public boolean isInfinite() {
556 return isInfinite(value);
557 }
558
559 /**
560 * Returns a string representation of this {@code Float} object.
561 * The primitive {@code float} value represented by this object
562 * is converted to a {@code String} exactly as if by the method
563 * {@code toString} of one argument.
564 *
565 * @return a {@code String} representation of this object.
566 * @see java.lang.Float#toString(float)
567 */
568 public String toString() {
569 return Float.toString(value);
570 }
571
572 /**
573 * Returns the value of this {@code Float} as a {@code byte} after
574 * a narrowing primitive conversion.
575 *
576 * @return the {@code float} value represented by this object
577 * converted to type {@code byte}
578 * @jls 5.1.3 Narrowing Primitive Conversions
579 */
580 public byte byteValue() {
581 return (byte)value;
582 }
583
584 /**
585 * Returns the value of this {@code Float} as a {@code short}
586 * after a narrowing primitive conversion.
587 *
588 * @return the {@code float} value represented by this object
589 * converted to type {@code short}
590 * @jls 5.1.3 Narrowing Primitive Conversions
591 * @since JDK1.1
592 */
593 public short shortValue() {
594 return (short)value;
595 }
596
597 /**
598 * Returns the value of this {@code Float} as an {@code int} after
599 * a narrowing primitive conversion.
600 *
601 * @return the {@code float} value represented by this object
602 * converted to type {@code int}
603 * @jls 5.1.3 Narrowing Primitive Conversions
604 */
605 public int intValue() {
606 return (int)value;
607 }
608
609 /**
610 * Returns value of this {@code Float} as a {@code long} after a
611 * narrowing primitive conversion.
612 *
613 * @return the {@code float} value represented by this object
614 * converted to type {@code long}
615 * @jls 5.1.3 Narrowing Primitive Conversions
616 */
617 public long longValue() {
618 return (long)value;
619 }
620
621 /**
622 * Returns the {@code float} value of this {@code Float} object.
623 *
624 * @return the {@code float} value represented by this object
625 */
626 public float floatValue() {
627 return value;
628 }
629
630 /**
631 * Returns the value of this {@code Float} as a {@code double}
632 * after a widening primitive conversion.
633 *
634 * @return the {@code float} value represented by this
635 * object converted to type {@code double}
636 * @jls 5.1.2 Widening Primitive Conversions
637 */
638 public double doubleValue() {
639 return (double)value;
640 }
641
642 /**
643 * Returns a hash code for this {@code Float} object. The
644 * result is the integer bit representation, exactly as produced
645 * by the method {@link #floatToIntBits(float)}, of the primitive
646 * {@code float} value represented by this {@code Float}
647 * object.
648 *
649 * @return a hash code value for this object.
650 */
651 public int hashCode() {
652 return floatToIntBits(value);
653 }
654
655 /**
656
657 * Compares this object against the specified object. The result
658 * is {@code true} if and only if the argument is not
659 * {@code null} and is a {@code Float} object that
660 * represents a {@code float} with the same value as the
661 * {@code float} represented by this object. For this
662 * purpose, two {@code float} values are considered to be the
663 * same if and only if the method {@link #floatToIntBits(float)}
664 * returns the identical {@code int} value when applied to
665 * each.
666 *
667 * <p>Note that in most cases, for two instances of class
668 * {@code Float}, {@code f1} and {@code f2}, the value
669 * of {@code f1.equals(f2)} is {@code true} if and only if
670 *
671 * <blockquote><pre>
672 * f1.floatValue() == f2.floatValue()
673 * </pre></blockquote>
674 *
675 * <p>also has the value {@code true}. However, there are two exceptions:
676 * <ul>
677 * <li>If {@code f1} and {@code f2} both represent
678 * {@code Float.NaN}, then the {@code equals} method returns
679 * {@code true}, even though {@code Float.NaN==Float.NaN}
680 * has the value {@code false}.
681 * <li>If {@code f1} represents {@code +0.0f} while
682 * {@code f2} represents {@code -0.0f}, or vice
683 * versa, the {@code equal} test has the value
684 * {@code false}, even though {@code 0.0f==-0.0f}
685 * has the value {@code true}.
686 * </ul>
687 *
688 * This definition allows hash tables to operate properly.
689 *
690 * @param obj the object to be compared
691 * @return {@code true} if the objects are the same;
692 * {@code false} otherwise.
693 * @see java.lang.Float#floatToIntBits(float)
694 */
695 public boolean equals(Object obj) {
696 return (obj instanceof Float)
697 && (floatToIntBits(((Float)obj).value) == floatToIntBits(value));
698 }
699
700 /**
701 * Returns a representation of the specified floating-point value
702 * according to the IEEE 754 floating-point "single format" bit
703 * layout.
704 *
705 * <p>Bit 31 (the bit that is selected by the mask
706 * {@code 0x80000000}) represents the sign of the floating-point
707 * number.
708 * Bits 30-23 (the bits that are selected by the mask
709 * {@code 0x7f800000}) represent the exponent.
710 * Bits 22-0 (the bits that are selected by the mask
711 * {@code 0x007fffff}) represent the significand (sometimes called
712 * the mantissa) of the floating-point number.
713 *
714 * <p>If the argument is positive infinity, the result is
715 * {@code 0x7f800000}.
716 *
717 * <p>If the argument is negative infinity, the result is
718 * {@code 0xff800000}.
719 *
720 * <p>If the argument is NaN, the result is {@code 0x7fc00000}.
721 *
722 * <p>In all cases, the result is an integer that, when given to the
723 * {@link #intBitsToFloat(int)} method, will produce a floating-point
724 * value the same as the argument to {@code floatToIntBits}
725 * (except all NaN values are collapsed to a single
726 * "canonical" NaN value).
727 *
728 * @param value a floating-point number.
729 * @return the bits that represent the floating-point number.
730 */
731 public static int floatToIntBits(float value) {
732 int result = floatToRawIntBits(value);
733 // Check for NaN based on values of bit fields, maximum
734 // exponent and nonzero significand.
735 if ( ((result & FloatConsts.EXP_BIT_MASK) ==
736 FloatConsts.EXP_BIT_MASK) &&
737 (result & FloatConsts.SIGNIF_BIT_MASK) != 0)
738 result = 0x7fc00000;
739 return result;
740 }
741
742 /**
743 * Returns a representation of the specified floating-point value
744 * according to the IEEE 754 floating-point "single format" bit
745 * layout, preserving Not-a-Number (NaN) values.
746 *
747 * <p>Bit 31 (the bit that is selected by the mask
748 * {@code 0x80000000}) represents the sign of the floating-point
749 * number.
750 * Bits 30-23 (the bits that are selected by the mask
751 * {@code 0x7f800000}) represent the exponent.
752 * Bits 22-0 (the bits that are selected by the mask
753 * {@code 0x007fffff}) represent the significand (sometimes called
754 * the mantissa) of the floating-point number.
755 *
756 * <p>If the argument is positive infinity, the result is
757 * {@code 0x7f800000}.
758 *
759 * <p>If the argument is negative infinity, the result is
760 * {@code 0xff800000}.
761 *
762 * <p>If the argument is NaN, the result is the integer representing
763 * the actual NaN value. Unlike the {@code floatToIntBits}
764 * method, {@code floatToRawIntBits} does not collapse all the
765 * bit patterns encoding a NaN to a single "canonical"
766 * NaN value.
767 *
768 * <p>In all cases, the result is an integer that, when given to the
769 * {@link #intBitsToFloat(int)} method, will produce a
770 * floating-point value the same as the argument to
771 * {@code floatToRawIntBits}.
772 *
773 * @param value a floating-point number.
774 * @return the bits that represent the floating-point number.
775 * @since 1.3
776 */
777 public static native int floatToRawIntBits(float value);
778
779 /**
780 * Returns the {@code float} value corresponding to a given
781 * bit representation.
782 * The argument is considered to be a representation of a
783 * floating-point value according to the IEEE 754 floating-point
784 * "single format" bit layout.
785 *
786 * <p>If the argument is {@code 0x7f800000}, the result is positive
787 * infinity.
788 *
789 * <p>If the argument is {@code 0xff800000}, the result is negative
790 * infinity.
791 *
792 * <p>If the argument is any value in the range
793 * {@code 0x7f800001} through {@code 0x7fffffff} or in
794 * the range {@code 0xff800001} through
795 * {@code 0xffffffff}, the result is a NaN. No IEEE 754
796 * floating-point operation provided by Java can distinguish
797 * between two NaN values of the same type with different bit
798 * patterns. Distinct values of NaN are only distinguishable by
799 * use of the {@code Float.floatToRawIntBits} method.
800 *
801 * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
802 * values that can be computed from the argument:
803 *
804 * <blockquote><pre>
805 * int s = ((bits >> 31) == 0) ? 1 : -1;
806 * int e = ((bits >> 23) & 0xff);
807 * int m = (e == 0) ?
808 * (bits & 0x7fffff) << 1 :
809 * (bits & 0x7fffff) | 0x800000;
810 * </pre></blockquote>
811 *
812 * Then the floating-point result equals the value of the mathematical
813 * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>.
814 *
815 * <p>Note that this method may not be able to return a
816 * {@code float} NaN with exactly same bit pattern as the
817 * {@code int} argument. IEEE 754 distinguishes between two
818 * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The
819 * differences between the two kinds of NaN are generally not
820 * visible in Java. Arithmetic operations on signaling NaNs turn
821 * them into quiet NaNs with a different, but often similar, bit
822 * pattern. However, on some processors merely copying a
823 * signaling NaN also performs that conversion. In particular,
824 * copying a signaling NaN to return it to the calling method may
825 * perform this conversion. So {@code intBitsToFloat} may
826 * not be able to return a {@code float} with a signaling NaN
827 * bit pattern. Consequently, for some {@code int} values,
828 * {@code floatToRawIntBits(intBitsToFloat(start))} may
829 * <i>not</i> equal {@code start}. Moreover, which
830 * particular bit patterns represent signaling NaNs is platform
831 * dependent; although all NaN bit patterns, quiet or signaling,
832 * must be in the NaN range identified above.
833 *
834 * @param bits an integer.
835 * @return the {@code float} floating-point value with the same bit
836 * pattern.
837 */
838 public static native float intBitsToFloat(int bits);
839
840 /**
841 * Compares two {@code Float} objects numerically. There are
842 * two ways in which comparisons performed by this method differ
843 * from those performed by the Java language numerical comparison
844 * operators ({@code <, <=, ==, >=, >}) when
845 * applied to primitive {@code float} values:
846 *
847 * <ul><li>
848 * {@code Float.NaN} is considered by this method to
849 * be equal to itself and greater than all other
850 * {@code float} values
851 * (including {@code Float.POSITIVE_INFINITY}).
852 * <li>
853 * {@code 0.0f} is considered by this method to be greater
854 * than {@code -0.0f}.
855 * </ul>
856 *
857 * This ensures that the <i>natural ordering</i> of {@code Float}
858 * objects imposed by this method is <i>consistent with equals</i>.
859 *
860 * @param anotherFloat the {@code Float} to be compared.
861 * @return the value {@code 0} if {@code anotherFloat} is
862 * numerically equal to this {@code Float}; a value
863 * less than {@code 0} if this {@code Float}
864 * is numerically less than {@code anotherFloat};
865 * and a value greater than {@code 0} if this
866 * {@code Float} is numerically greater than
867 * {@code anotherFloat}.
868 *
869 * @since 1.2
870 * @see Comparable#compareTo(Object)
871 */
872 public int compareTo(Float anotherFloat) {
873 return Float.compare(value, anotherFloat.value);
874 }
875
876 /**
877 * Compares the two specified {@code float} values. The sign
878 * of the integer value returned is the same as that of the
879 * integer that would be returned by the call:
880 * <pre>
881 * new Float(f1).compareTo(new Float(f2))
882 * </pre>
883 *
884 * @param f1 the first {@code float} to compare.
885 * @param f2 the second {@code float} to compare.
886 * @return the value {@code 0} if {@code f1} is
887 * numerically equal to {@code f2}; a value less than
888 * {@code 0} if {@code f1} is numerically less than
889 * {@code f2}; and a value greater than {@code 0}
890 * if {@code f1} is numerically greater than
891 * {@code f2}.
892 * @since 1.4
893 */
894 public static int compare(float f1, float f2) {
895 if (f1 < f2)
896 return -1; // Neither val is NaN, thisVal is smaller
897 if (f1 > f2)
898 return 1; // Neither val is NaN, thisVal is larger
899
900 // Cannot use floatToRawIntBits because of possibility of NaNs.
901 int thisBits = Float.floatToIntBits(f1);
902 int anotherBits = Float.floatToIntBits(f2);
903
904 return (thisBits == anotherBits ? 0 : // Values are equal
905 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
906 1)); // (0.0, -0.0) or (NaN, !NaN)
907 }
908
909 /** use serialVersionUID from JDK 1.0.2 for interoperability */
910 private static final long serialVersionUID = -2671257302660747028L;
911 }