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    4    *
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    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
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   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).
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   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>)&middot;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>'&#92;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>'&#92;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>&le;
  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 &le; <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>'&#92;u002E'</code>), followed by
  170        *      decimal digits representing the fractional part of
  171        *      <i>a</i>, followed by the letter '{@code E}'
  172        *      (<code>'&#92;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>'&#92;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&trade; 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 &gt;&gt; 31) == 0) ? 1 : -1;
  787        * int e = ((bits &gt;&gt; 23) & 0xff);
  788        * int m = (e == 0) ?
  789        *                 (bits & 0x7fffff) &lt;&lt; 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>&middot;<i>m</i>&middot;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   }

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