1 /*
   2  * Copyright (c) 1994, 2013, 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
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  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>)&middot;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 number of bytes used to represent a {@code float} value.
 125      *
 126      * @since 1.8
 127      */
 128     public static final int BYTES = SIZE / Byte.SIZE;
 129 
 130     /**
 131      * The {@code Class} instance representing the primitive type
 132      * {@code float}.
 133      *
 134      * @since JDK1.1
 135      */
 136     @SuppressWarnings("unchecked")
 137     public static final Class<Float> TYPE = (Class<Float>) Class.getPrimitiveClass("float");
 138 
 139     /**
 140      * Returns a string representation of the {@code float}
 141      * argument. All characters mentioned below are ASCII characters.
 142      * <ul>
 143      * <li>If the argument is NaN, the result is the string
 144      * "{@code NaN}".
 145      * <li>Otherwise, the result is a string that represents the sign and
 146      *     magnitude (absolute value) of the argument. If the sign is
 147      *     negative, the first character of the result is
 148      *     '{@code -}' ({@code '\u005Cu002D'}); if the sign is
 149      *     positive, no sign character appears in the result. As for
 150      *     the magnitude <i>m</i>:
 151      * <ul>
 152      * <li>If <i>m</i> is infinity, it is represented by the characters
 153      *     {@code "Infinity"}; thus, positive infinity produces
 154      *     the result {@code "Infinity"} and negative infinity
 155      *     produces the result {@code "-Infinity"}.
 156      * <li>If <i>m</i> is zero, it is represented by the characters
 157      *     {@code "0.0"}; thus, negative zero produces the result
 158      *     {@code "-0.0"} and positive zero produces the result
 159      *     {@code "0.0"}.
 160      * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but
 161      *      less than 10<sup>7</sup>, then it is represented as the
 162      *      integer part of <i>m</i>, in decimal form with no leading
 163      *      zeroes, followed by '{@code .}'
 164      *      ({@code '\u005Cu002E'}), followed by one or more
 165      *      decimal digits representing the fractional part of
 166      *      <i>m</i>.
 167      * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or
 168      *      equal to 10<sup>7</sup>, then it is represented in
 169      *      so-called "computerized scientific notation." Let <i>n</i>
 170      *      be the unique integer such that 10<sup><i>n</i> </sup>&le;
 171      *      <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i>
 172      *      be the mathematically exact quotient of <i>m</i> and
 173      *      10<sup><i>n</i></sup> so that 1 &le; <i>a</i> {@literal <} 10.
 174      *      The magnitude is then represented as the integer part of
 175      *      <i>a</i>, as a single decimal digit, followed by
 176      *      '{@code .}' ({@code '\u005Cu002E'}), followed by
 177      *      decimal digits representing the fractional part of
 178      *      <i>a</i>, followed by the letter '{@code E}'
 179      *      ({@code '\u005Cu0045'}), followed by a representation
 180      *      of <i>n</i> as a decimal integer, as produced by the
 181      *      method {@link java.lang.Integer#toString(int)}.
 182      *
 183      * </ul>
 184      * </ul>
 185      * How many digits must be printed for the fractional part of
 186      * <i>m</i> or <i>a</i>? There must be at least one digit
 187      * to represent the fractional part, and beyond that as many, but
 188      * only as many, more digits as are needed to uniquely distinguish
 189      * the argument value from adjacent values of type
 190      * {@code float}. That is, suppose that <i>x</i> is the
 191      * exact mathematical value represented by the decimal
 192      * representation produced by this method for a finite nonzero
 193      * argument <i>f</i>. Then <i>f</i> must be the {@code float}
 194      * value nearest to <i>x</i>; or, if two {@code float} values are
 195      * equally close to <i>x</i>, then <i>f</i> must be one of
 196      * them and the least significant bit of the significand of
 197      * <i>f</i> must be {@code 0}.
 198      *
 199      * <p>To create localized string representations of a floating-point
 200      * value, use subclasses of {@link java.text.NumberFormat}.
 201      *
 202      * @param   f   the float to be converted.
 203      * @return a string representation of the argument.
 204      */
 205     public static String toString(float f) {
 206         return FloatingDecimal.toJavaFormatString(f);
 207     }
 208 
 209     /**
 210      * Returns a hexadecimal string representation of the
 211      * {@code float} argument. All characters mentioned below are
 212      * ASCII characters.
 213      *
 214      * <ul>
 215      * <li>If the argument is NaN, the result is the string
 216      *     "{@code NaN}".
 217      * <li>Otherwise, the result is a string that represents the sign and
 218      * magnitude (absolute value) of the argument. If the sign is negative,
 219      * the first character of the result is '{@code -}'
 220      * ({@code '\u005Cu002D'}); if the sign is positive, no sign character
 221      * appears in the result. As for the magnitude <i>m</i>:
 222      *
 223      * <ul>
 224      * <li>If <i>m</i> is infinity, it is represented by the string
 225      * {@code "Infinity"}; thus, positive infinity produces the
 226      * result {@code "Infinity"} and negative infinity produces
 227      * the result {@code "-Infinity"}.
 228      *
 229      * <li>If <i>m</i> is zero, it is represented by the string
 230      * {@code "0x0.0p0"}; thus, negative zero produces the result
 231      * {@code "-0x0.0p0"} and positive zero produces the result
 232      * {@code "0x0.0p0"}.
 233      *
 234      * <li>If <i>m</i> is a {@code float} value with a
 235      * normalized representation, substrings are used to represent the
 236      * significand and exponent fields.  The significand is
 237      * represented by the characters {@code "0x1."}
 238      * followed by a lowercase hexadecimal representation of the rest
 239      * of the significand as a fraction.  Trailing zeros in the
 240      * hexadecimal representation are removed unless all the digits
 241      * are zero, in which case a single zero is used. Next, the
 242      * exponent is represented by {@code "p"} followed
 243      * by a decimal string of the unbiased exponent as if produced by
 244      * a call to {@link Integer#toString(int) Integer.toString} on the
 245      * exponent value.
 246      *
 247      * <li>If <i>m</i> is a {@code float} value with a subnormal
 248      * representation, the significand is represented by the
 249      * characters {@code "0x0."} followed by a
 250      * hexadecimal representation of the rest of the significand as a
 251      * fraction.  Trailing zeros in the hexadecimal representation are
 252      * removed. Next, the exponent is represented by
 253      * {@code "p-126"}.  Note that there must be at
 254      * least one nonzero digit in a subnormal significand.
 255      *
 256      * </ul>
 257      *
 258      * </ul>
 259      *
 260      * <table border>
 261      * <caption><h3>Examples</h3></caption>
 262      * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
 263      * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
 264      * <tr><td>{@code -1.0}</td>        <td>{@code -0x1.0p0}</td>
 265      * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
 266      * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
 267      * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
 268      * <tr><td>{@code 0.25}</td>        <td>{@code 0x1.0p-2}</td>
 269      * <tr><td>{@code Float.MAX_VALUE}</td>
 270      *     <td>{@code 0x1.fffffep127}</td>
 271      * <tr><td>{@code Minimum Normal Value}</td>
 272      *     <td>{@code 0x1.0p-126}</td>
 273      * <tr><td>{@code Maximum Subnormal Value}</td>
 274      *     <td>{@code 0x0.fffffep-126}</td>
 275      * <tr><td>{@code Float.MIN_VALUE}</td>
 276      *     <td>{@code 0x0.000002p-126}</td>
 277      * </table>
 278      * @param   f   the {@code float} to be converted.
 279      * @return a hex string representation of the argument.
 280      * @since 1.5
 281      * @author Joseph D. Darcy
 282      */
 283     public static String toHexString(float f) {
 284         if (Math.abs(f) < FloatConsts.MIN_NORMAL
 285             &&  f != 0.0f ) {// float subnormal
 286             // Adjust exponent to create subnormal double, then
 287             // replace subnormal double exponent with subnormal float
 288             // exponent
 289             String s = Double.toHexString(Math.scalb((double)f,
 290                                                      /* -1022+126 */
 291                                                      DoubleConsts.MIN_EXPONENT-
 292                                                      FloatConsts.MIN_EXPONENT));
 293             return s.replaceFirst("p-1022$", "p-126");
 294         }
 295         else // double string will be the same as float string
 296             return Double.toHexString(f);
 297     }
 298 
 299     /**
 300      * Returns a {@code Float} object holding the
 301      * {@code float} value represented by the argument string
 302      * {@code s}.
 303      *
 304      * <p>If {@code s} is {@code null}, then a
 305      * {@code NullPointerException} is thrown.
 306      *
 307      * <p>Leading and trailing whitespace characters in {@code s}
 308      * are ignored.  Whitespace is removed as if by the {@link
 309      * String#trim} method; that is, both ASCII space and control
 310      * characters are removed. The rest of {@code s} should
 311      * constitute a <i>FloatValue</i> as described by the lexical
 312      * syntax rules:
 313      *
 314      * <blockquote>
 315      * <dl>
 316      * <dt><i>FloatValue:</i>
 317      * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
 318      * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
 319      * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
 320      * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
 321      * <dd><i>SignedInteger</i>
 322      * </dl>
 323      *
 324      * <p>
 325      *
 326      * <dl>
 327      * <dt><i>HexFloatingPointLiteral</i>:
 328      * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
 329      * </dl>
 330      *
 331      * <p>
 332      *
 333      * <dl>
 334      * <dt><i>HexSignificand:</i>
 335      * <dd><i>HexNumeral</i>
 336      * <dd><i>HexNumeral</i> {@code .}
 337      * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
 338      *     </i>{@code .}<i> HexDigits</i>
 339      * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
 340      *     </i>{@code .} <i>HexDigits</i>
 341      * </dl>
 342      *
 343      * <p>
 344      *
 345      * <dl>
 346      * <dt><i>BinaryExponent:</i>
 347      * <dd><i>BinaryExponentIndicator SignedInteger</i>
 348      * </dl>
 349      *
 350      * <p>
 351      *
 352      * <dl>
 353      * <dt><i>BinaryExponentIndicator:</i>
 354      * <dd>{@code p}
 355      * <dd>{@code P}
 356      * </dl>
 357      *
 358      * </blockquote>
 359      *
 360      * where <i>Sign</i>, <i>FloatingPointLiteral</i>,
 361      * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and
 362      * <i>FloatTypeSuffix</i> are as defined in the lexical structure
 363      * sections of
 364      * <cite>The Java&trade; Language Specification</cite>,
 365      * except that underscores are not accepted between digits.
 366      * If {@code s} does not have the form of
 367      * a <i>FloatValue</i>, then a {@code NumberFormatException}
 368      * is thrown. Otherwise, {@code s} is regarded as
 369      * representing an exact decimal value in the usual
 370      * "computerized scientific notation" or as an exact
 371      * hexadecimal value; this exact numerical value is then
 372      * conceptually converted to an "infinitely precise"
 373      * binary value that is then rounded to type {@code float}
 374      * by the usual round-to-nearest rule of IEEE 754 floating-point
 375      * arithmetic, which includes preserving the sign of a zero
 376      * value.
 377      *
 378      * Note that the round-to-nearest rule also implies overflow and
 379      * underflow behaviour; if the exact value of {@code s} is large
 380      * enough in magnitude (greater than or equal to ({@link
 381      * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2),
 382      * rounding to {@code float} will result in an infinity and if the
 383      * exact value of {@code s} is small enough in magnitude (less
 384      * than or equal to {@link #MIN_VALUE}/2), rounding to float will
 385      * result in a zero.
 386      *
 387      * Finally, after rounding a {@code Float} object representing
 388      * this {@code float} value is returned.
 389      *
 390      * <p>To interpret localized string representations of a
 391      * floating-point value, use subclasses of {@link
 392      * java.text.NumberFormat}.
 393      *
 394      * <p>Note that trailing format specifiers, specifiers that
 395      * determine the type of a floating-point literal
 396      * ({@code 1.0f} is a {@code float} value;
 397      * {@code 1.0d} is a {@code double} value), do
 398      * <em>not</em> influence the results of this method.  In other
 399      * words, the numerical value of the input string is converted
 400      * directly to the target floating-point type.  In general, the
 401      * two-step sequence of conversions, string to {@code double}
 402      * followed by {@code double} to {@code float}, is
 403      * <em>not</em> equivalent to converting a string directly to
 404      * {@code float}.  For example, if first converted to an
 405      * intermediate {@code double} and then to
 406      * {@code float}, the string<br>
 407      * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br>
 408      * results in the {@code float} value
 409      * {@code 1.0000002f}; if the string is converted directly to
 410      * {@code float}, <code>1.000000<b>1</b>f</code> results.
 411      *
 412      * <p>To avoid calling this method on an invalid string and having
 413      * a {@code NumberFormatException} be thrown, the documentation
 414      * for {@link Double#valueOf Double.valueOf} lists a regular
 415      * expression which can be used to screen the input.
 416      *
 417      * @param   s   the string to be parsed.
 418      * @return  a {@code Float} object holding the value
 419      *          represented by the {@code String} argument.
 420      * @throws  NumberFormatException  if the string does not contain a
 421      *          parsable number.
 422      */
 423     public static Float valueOf(String s) throws NumberFormatException {
 424         return new Float(parseFloat(s));
 425     }
 426 
 427     /**
 428      * Returns a {@code Float} instance representing the specified
 429      * {@code float} value.
 430      * If a new {@code Float} instance is not required, this method
 431      * should generally be used in preference to the constructor
 432      * {@link #Float(float)}, as this method is likely to yield
 433      * significantly better space and time performance by caching
 434      * frequently requested values.
 435      *
 436      * @param  f a float value.
 437      * @return a {@code Float} instance representing {@code f}.
 438      * @since  1.5
 439      */
 440     public static Float valueOf(float f) {
 441         return new Float(f);
 442     }
 443 
 444     /**
 445      * Returns a new {@code float} initialized to the value
 446      * represented by the specified {@code String}, as performed
 447      * by the {@code valueOf} method of class {@code Float}.
 448      *
 449      * @param  s the string to be parsed.
 450      * @return the {@code float} value represented by the string
 451      *         argument.
 452      * @throws NullPointerException  if the string is null
 453      * @throws NumberFormatException if the string does not contain a
 454      *               parsable {@code float}.
 455      * @see    java.lang.Float#valueOf(String)
 456      * @since 1.2
 457      */
 458     public static float parseFloat(String s) throws NumberFormatException {
 459         return FloatingDecimal.parseFloat(s);
 460     }
 461 
 462     /**
 463      * Returns {@code true} if the specified number is a
 464      * Not-a-Number (NaN) value, {@code false} otherwise.
 465      *
 466      * @param   v   the value to be tested.
 467      * @return  {@code true} if the argument is NaN;
 468      *          {@code false} otherwise.
 469      */
 470     public static boolean isNaN(float v) {
 471         return (v != v);
 472     }
 473 
 474     /**
 475      * Returns {@code true} if the specified number is infinitely
 476      * large in magnitude, {@code false} otherwise.
 477      *
 478      * @param   v   the value to be tested.
 479      * @return  {@code true} if the argument is positive infinity or
 480      *          negative infinity; {@code false} otherwise.
 481      */
 482     public static boolean isInfinite(float v) {
 483         return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
 484     }
 485 
 486 
 487     /**
 488      * Returns {@code true} if the argument is a finite floating-point
 489      * value; returns {@code false} otherwise (for NaN and infinity
 490      * arguments).
 491      *
 492      * @param f the {@code float} value to be tested
 493      * @return {@code true} if the argument is a finite
 494      * floating-point value, {@code false} otherwise.
 495      * @since 1.8
 496      */
 497      public static boolean isFinite(float f) {
 498         return Math.abs(f) <= FloatConsts.MAX_VALUE;
 499     }
 500 
 501     /**
 502      * The value of the Float.
 503      *
 504      * @serial
 505      */
 506     private final float value;
 507 
 508     /**
 509      * Constructs a newly allocated {@code Float} object that
 510      * represents the primitive {@code float} argument.
 511      *
 512      * @param   value   the value to be represented by the {@code Float}.
 513      */
 514     public Float(float value) {
 515         this.value = value;
 516     }
 517 
 518     /**
 519      * Constructs a newly allocated {@code Float} object that
 520      * represents the argument converted to type {@code float}.
 521      *
 522      * @param   value   the value to be represented by the {@code Float}.
 523      */
 524     public Float(double value) {
 525         this.value = (float)value;
 526     }
 527 
 528     /**
 529      * Constructs a newly allocated {@code Float} object that
 530      * represents the floating-point value of type {@code float}
 531      * represented by the string. The string is converted to a
 532      * {@code float} value as if by the {@code valueOf} method.
 533      *
 534      * @param      s   a string to be converted to a {@code Float}.
 535      * @throws  NumberFormatException  if the string does not contain a
 536      *               parsable number.
 537      * @see        java.lang.Float#valueOf(java.lang.String)
 538      */
 539     public Float(String s) throws NumberFormatException {
 540         value = parseFloat(s);
 541     }
 542 
 543     /**
 544      * Returns {@code true} if this {@code Float} value is a
 545      * Not-a-Number (NaN), {@code false} otherwise.
 546      *
 547      * @return  {@code true} if the value represented by this object is
 548      *          NaN; {@code false} otherwise.
 549      */
 550     public boolean isNaN() {
 551         return isNaN(value);
 552     }
 553 
 554     /**
 555      * Returns {@code true} if this {@code Float} value is
 556      * infinitely large in magnitude, {@code false} otherwise.
 557      *
 558      * @return  {@code true} if the value represented by this object is
 559      *          positive infinity or negative infinity;
 560      *          {@code false} otherwise.
 561      */
 562     public boolean isInfinite() {
 563         return isInfinite(value);
 564     }
 565 
 566     /**
 567      * Returns a string representation of this {@code Float} object.
 568      * The primitive {@code float} value represented by this object
 569      * is converted to a {@code String} exactly as if by the method
 570      * {@code toString} of one argument.
 571      *
 572      * @return  a {@code String} representation of this object.
 573      * @see java.lang.Float#toString(float)
 574      */
 575     public String toString() {
 576         return Float.toString(value);
 577     }
 578 
 579     /**
 580      * Returns the value of this {@code Float} as a {@code byte} after
 581      * a narrowing primitive conversion.
 582      *
 583      * @return  the {@code float} value represented by this object
 584      *          converted to type {@code byte}
 585      * @jls 5.1.3 Narrowing Primitive Conversions
 586      */
 587     public byte byteValue() {
 588         return (byte)value;
 589     }
 590 
 591     /**
 592      * Returns the value of this {@code Float} as a {@code short}
 593      * after a narrowing primitive conversion.
 594      *
 595      * @return  the {@code float} value represented by this object
 596      *          converted to type {@code short}
 597      * @jls 5.1.3 Narrowing Primitive Conversions
 598      * @since JDK1.1
 599      */
 600     public short shortValue() {
 601         return (short)value;
 602     }
 603 
 604     /**
 605      * Returns the value of this {@code Float} as an {@code int} after
 606      * a narrowing primitive conversion.
 607      *
 608      * @return  the {@code float} value represented by this object
 609      *          converted to type {@code int}
 610      * @jls 5.1.3 Narrowing Primitive Conversions
 611      */
 612     public int intValue() {
 613         return (int)value;
 614     }
 615 
 616     /**
 617      * Returns value of this {@code Float} as a {@code long} after a
 618      * narrowing primitive conversion.
 619      *
 620      * @return  the {@code float} value represented by this object
 621      *          converted to type {@code long}
 622      * @jls 5.1.3 Narrowing Primitive Conversions
 623      */
 624     public long longValue() {
 625         return (long)value;
 626     }
 627 
 628     /**
 629      * Returns the {@code float} value of this {@code Float} object.
 630      *
 631      * @return the {@code float} value represented by this object
 632      */
 633     public float floatValue() {
 634         return value;
 635     }
 636 
 637     /**
 638      * Returns the value of this {@code Float} as a {@code double}
 639      * after a widening primitive conversion.
 640      *
 641      * @return the {@code float} value represented by this
 642      *         object converted to type {@code double}
 643      * @jls 5.1.2 Widening Primitive Conversions
 644      */
 645     public double doubleValue() {
 646         return (double)value;
 647     }
 648 
 649     /**
 650      * Returns a hash code for this {@code Float} object. The
 651      * result is the integer bit representation, exactly as produced
 652      * by the method {@link #floatToIntBits(float)}, of the primitive
 653      * {@code float} value represented by this {@code Float}
 654      * object.
 655      *
 656      * @return a hash code value for this object.
 657      */
 658     @Override
 659     public int hashCode() {
 660         return Float.hashCode(value);
 661     }
 662 
 663     /**
 664      * Returns a hash code for a {@code float} value; compatible with
 665      * {@code Float.hashCode()}.
 666      *
 667      * @param value the value to hash
 668      * @return a hash code value for a {@code float} value.
 669      * @since 1.8
 670      */
 671     public static int hashCode(float value) {
 672         return floatToIntBits(value);
 673     }
 674 
 675     /**
 676 
 677      * Compares this object against the specified object.  The result
 678      * is {@code true} if and only if the argument is not
 679      * {@code null} and is a {@code Float} object that
 680      * represents a {@code float} with the same value as the
 681      * {@code float} represented by this object. For this
 682      * purpose, two {@code float} values are considered to be the
 683      * same if and only if the method {@link #floatToIntBits(float)}
 684      * returns the identical {@code int} value when applied to
 685      * each.
 686      *
 687      * <p>Note that in most cases, for two instances of class
 688      * {@code Float}, {@code f1} and {@code f2}, the value
 689      * of {@code f1.equals(f2)} is {@code true} if and only if
 690      *
 691      * <blockquote><pre>
 692      *   f1.floatValue() == f2.floatValue()
 693      * </pre></blockquote>
 694      *
 695      * <p>also has the value {@code true}. However, there are two exceptions:
 696      * <ul>
 697      * <li>If {@code f1} and {@code f2} both represent
 698      *     {@code Float.NaN}, then the {@code equals} method returns
 699      *     {@code true}, even though {@code Float.NaN==Float.NaN}
 700      *     has the value {@code false}.
 701      * <li>If {@code f1} represents {@code +0.0f} while
 702      *     {@code f2} represents {@code -0.0f}, or vice
 703      *     versa, the {@code equal} test has the value
 704      *     {@code false}, even though {@code 0.0f==-0.0f}
 705      *     has the value {@code true}.
 706      * </ul>
 707      *
 708      * This definition allows hash tables to operate properly.
 709      *
 710      * @param obj the object to be compared
 711      * @return  {@code true} if the objects are the same;
 712      *          {@code false} otherwise.
 713      * @see java.lang.Float#floatToIntBits(float)
 714      */
 715     public boolean equals(Object obj) {
 716         return (obj instanceof Float)
 717                && (floatToIntBits(((Float)obj).value) == floatToIntBits(value));
 718     }
 719 
 720     /**
 721      * Returns a representation of the specified floating-point value
 722      * according to the IEEE 754 floating-point "single format" bit
 723      * layout.
 724      *
 725      * <p>Bit 31 (the bit that is selected by the mask
 726      * {@code 0x80000000}) represents the sign of the floating-point
 727      * number.
 728      * Bits 30-23 (the bits that are selected by the mask
 729      * {@code 0x7f800000}) represent the exponent.
 730      * Bits 22-0 (the bits that are selected by the mask
 731      * {@code 0x007fffff}) represent the significand (sometimes called
 732      * the mantissa) of the floating-point number.
 733      *
 734      * <p>If the argument is positive infinity, the result is
 735      * {@code 0x7f800000}.
 736      *
 737      * <p>If the argument is negative infinity, the result is
 738      * {@code 0xff800000}.
 739      *
 740      * <p>If the argument is NaN, the result is {@code 0x7fc00000}.
 741      *
 742      * <p>In all cases, the result is an integer that, when given to the
 743      * {@link #intBitsToFloat(int)} method, will produce a floating-point
 744      * value the same as the argument to {@code floatToIntBits}
 745      * (except all NaN values are collapsed to a single
 746      * "canonical" NaN value).
 747      *
 748      * @param   value   a floating-point number.
 749      * @return the bits that represent the floating-point number.
 750      */
 751     public static int floatToIntBits(float value) {
 752         int result = floatToRawIntBits(value);
 753         // Check for NaN based on values of bit fields, maximum
 754         // exponent and nonzero significand.
 755         if ( ((result & FloatConsts.EXP_BIT_MASK) ==
 756               FloatConsts.EXP_BIT_MASK) &&
 757              (result & FloatConsts.SIGNIF_BIT_MASK) != 0)
 758             result = 0x7fc00000;
 759         return result;
 760     }
 761 
 762     /**
 763      * Returns a representation of the specified floating-point value
 764      * according to the IEEE 754 floating-point "single format" bit
 765      * layout, preserving Not-a-Number (NaN) values.
 766      *
 767      * <p>Bit 31 (the bit that is selected by the mask
 768      * {@code 0x80000000}) represents the sign of the floating-point
 769      * number.
 770      * Bits 30-23 (the bits that are selected by the mask
 771      * {@code 0x7f800000}) represent the exponent.
 772      * Bits 22-0 (the bits that are selected by the mask
 773      * {@code 0x007fffff}) represent the significand (sometimes called
 774      * the mantissa) of the floating-point number.
 775      *
 776      * <p>If the argument is positive infinity, the result is
 777      * {@code 0x7f800000}.
 778      *
 779      * <p>If the argument is negative infinity, the result is
 780      * {@code 0xff800000}.
 781      *
 782      * <p>If the argument is NaN, the result is the integer representing
 783      * the actual NaN value.  Unlike the {@code floatToIntBits}
 784      * method, {@code floatToRawIntBits} does not collapse all the
 785      * bit patterns encoding a NaN to a single "canonical"
 786      * NaN value.
 787      *
 788      * <p>In all cases, the result is an integer that, when given to the
 789      * {@link #intBitsToFloat(int)} method, will produce a
 790      * floating-point value the same as the argument to
 791      * {@code floatToRawIntBits}.
 792      *
 793      * @param   value   a floating-point number.
 794      * @return the bits that represent the floating-point number.
 795      * @since 1.3
 796      */
 797     public static native int floatToRawIntBits(float value);
 798 
 799     /**
 800      * Returns the {@code float} value corresponding to a given
 801      * bit representation.
 802      * The argument is considered to be a representation of a
 803      * floating-point value according to the IEEE 754 floating-point
 804      * "single format" bit layout.
 805      *
 806      * <p>If the argument is {@code 0x7f800000}, the result is positive
 807      * infinity.
 808      *
 809      * <p>If the argument is {@code 0xff800000}, the result is negative
 810      * infinity.
 811      *
 812      * <p>If the argument is any value in the range
 813      * {@code 0x7f800001} through {@code 0x7fffffff} or in
 814      * the range {@code 0xff800001} through
 815      * {@code 0xffffffff}, the result is a NaN.  No IEEE 754
 816      * floating-point operation provided by Java can distinguish
 817      * between two NaN values of the same type with different bit
 818      * patterns.  Distinct values of NaN are only distinguishable by
 819      * use of the {@code Float.floatToRawIntBits} method.
 820      *
 821      * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
 822      * values that can be computed from the argument:
 823      *
 824      * <blockquote><pre>{@code
 825      * int s = ((bits >> 31) == 0) ? 1 : -1;
 826      * int e = ((bits >> 23) & 0xff);
 827      * int m = (e == 0) ?
 828      *                 (bits & 0x7fffff) << 1 :
 829      *                 (bits & 0x7fffff) | 0x800000;
 830      * }</pre></blockquote>
 831      *
 832      * Then the floating-point result equals the value of the mathematical
 833      * expression <i>s</i>&middot;<i>m</i>&middot;2<sup><i>e</i>-150</sup>.
 834      *
 835      * <p>Note that this method may not be able to return a
 836      * {@code float} NaN with exactly same bit pattern as the
 837      * {@code int} argument.  IEEE 754 distinguishes between two
 838      * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>.  The
 839      * differences between the two kinds of NaN are generally not
 840      * visible in Java.  Arithmetic operations on signaling NaNs turn
 841      * them into quiet NaNs with a different, but often similar, bit
 842      * pattern.  However, on some processors merely copying a
 843      * signaling NaN also performs that conversion.  In particular,
 844      * copying a signaling NaN to return it to the calling method may
 845      * perform this conversion.  So {@code intBitsToFloat} may
 846      * not be able to return a {@code float} with a signaling NaN
 847      * bit pattern.  Consequently, for some {@code int} values,
 848      * {@code floatToRawIntBits(intBitsToFloat(start))} may
 849      * <i>not</i> equal {@code start}.  Moreover, which
 850      * particular bit patterns represent signaling NaNs is platform
 851      * dependent; although all NaN bit patterns, quiet or signaling,
 852      * must be in the NaN range identified above.
 853      *
 854      * @param   bits   an integer.
 855      * @return  the {@code float} floating-point value with the same bit
 856      *          pattern.
 857      */
 858     public static native float intBitsToFloat(int bits);
 859 
 860     /**
 861      * Compares two {@code Float} objects numerically.  There are
 862      * two ways in which comparisons performed by this method differ
 863      * from those performed by the Java language numerical comparison
 864      * operators ({@code <, <=, ==, >=, >}) when
 865      * applied to primitive {@code float} values:
 866      *
 867      * <ul><li>
 868      *          {@code Float.NaN} is considered by this method to
 869      *          be equal to itself and greater than all other
 870      *          {@code float} values
 871      *          (including {@code Float.POSITIVE_INFINITY}).
 872      * <li>
 873      *          {@code 0.0f} is considered by this method to be greater
 874      *          than {@code -0.0f}.
 875      * </ul>
 876      *
 877      * This ensures that the <i>natural ordering</i> of {@code Float}
 878      * objects imposed by this method is <i>consistent with equals</i>.
 879      *
 880      * @param   anotherFloat   the {@code Float} to be compared.
 881      * @return  the value {@code 0} if {@code anotherFloat} is
 882      *          numerically equal to this {@code Float}; a value
 883      *          less than {@code 0} if this {@code Float}
 884      *          is numerically less than {@code anotherFloat};
 885      *          and a value greater than {@code 0} if this
 886      *          {@code Float} is numerically greater than
 887      *          {@code anotherFloat}.
 888      *
 889      * @since   1.2
 890      * @see Comparable#compareTo(Object)
 891      */
 892     public int compareTo(Float anotherFloat) {
 893         return Float.compare(value, anotherFloat.value);
 894     }
 895 
 896     /**
 897      * Compares the two specified {@code float} values. The sign
 898      * of the integer value returned is the same as that of the
 899      * integer that would be returned by the call:
 900      * <pre>
 901      *    new Float(f1).compareTo(new Float(f2))
 902      * </pre>
 903      *
 904      * @param   f1        the first {@code float} to compare.
 905      * @param   f2        the second {@code float} to compare.
 906      * @return  the value {@code 0} if {@code f1} is
 907      *          numerically equal to {@code f2}; a value less than
 908      *          {@code 0} if {@code f1} is numerically less than
 909      *          {@code f2}; and a value greater than {@code 0}
 910      *          if {@code f1} is numerically greater than
 911      *          {@code f2}.
 912      * @since 1.4
 913      */
 914     public static int compare(float f1, float f2) {
 915         if (f1 < f2)
 916             return -1;           // Neither val is NaN, thisVal is smaller
 917         if (f1 > f2)
 918             return 1;            // Neither val is NaN, thisVal is larger
 919 
 920         // Cannot use floatToRawIntBits because of possibility of NaNs.
 921         int thisBits    = Float.floatToIntBits(f1);
 922         int anotherBits = Float.floatToIntBits(f2);
 923 
 924         return (thisBits == anotherBits ?  0 : // Values are equal
 925                 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
 926                  1));                          // (0.0, -0.0) or (NaN, !NaN)
 927     }
 928 
 929     /**
 930      * Adds two {@code float} values together as per the + operator.
 931      *
 932      * @param a the first operand
 933      * @param b the second operand
 934      * @return the sum of {@code a} and {@code b}
 935      * @jls 4.2.4 Floating-Point Operations
 936      * @see java.util.function.BinaryOperator
 937      * @since 1.8
 938      */
 939     public static float sum(float a, float b) {
 940         return a + b;
 941     }
 942 
 943     /**
 944      * Returns the greater of two {@code float} values
 945      * as if by calling {@link Math#max(float, float) Math.max}.
 946      *
 947      * @param a the first operand
 948      * @param b the second operand
 949      * @return the greater of {@code a} and {@code b}
 950      * @see java.util.function.BinaryOperator
 951      * @since 1.8
 952      */
 953     public static float max(float a, float b) {
 954         return Math.max(a, b);
 955     }
 956 
 957     /**
 958      * Returns the smaller of two {@code float} values
 959      * as if by calling {@link Math#min(float, float) Math.min}.
 960      *
 961      * @param a the first operand
 962      * @param b the second operand
 963      * @return the smaller of {@code a} and {@code b}
 964      * @see java.util.function.BinaryOperator
 965      * @since 1.8
 966      */
 967     public static float min(float a, float b) {
 968         return Math.min(a, b);
 969     }
 970 
 971     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 972     private static final long serialVersionUID = -2671257302660747028L;
 973 }