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JDK 1.6
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/* * @(#)Float.java 1.101 06/04/07 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.lang; import sun.misc.FloatingDecimal; import sun.misc.FpUtils; import sun.misc.FloatConsts; import sun.misc.DoubleConsts; /** * The <code>Float</code> class wraps a value of primitive type * <code>float</code> in an object. An object of type * <code>Float</code> contains a single field whose type is * <code>float</code>. * <p> * In addition, this class provides several methods for converting a * <code>float</code> to a <code>String</code> and a * <code>String</code> to a <code>float</code>, as well as other * constants and methods useful when dealing with a * <code>float</code>. * * @author Lee Boynton * @author Arthur van Hoff * @author Joseph D. Darcy * @version 1.101, 04/07/06 * @since JDK1.0 */ public final class Float extends Number implements Comparable<Float> { /** * A constant holding the positive infinity of type * <code>float</code>. It is equal to the value returned by * <code>Float.intBitsToFloat(0x7f800000)</code>. */ public static final float POSITIVE_INFINITY = 1.0f / 0.0f; /** * A constant holding the negative infinity of type * <code>float</code>. It is equal to the value returned by * <code>Float.intBitsToFloat(0xff800000)</code>. */ public static final float NEGATIVE_INFINITY = -1.0f / 0.0f; /** * A constant holding a Not-a-Number (NaN) value of type * <code>float</code>. It is equivalent to the value returned by * <code>Float.intBitsToFloat(0x7fc00000)</code>. */ public static final float NaN = 0.0f / 0.0f; /** * A constant holding the largest positive finite value of type * <code>float</code>, (2-2<sup>-23</sup>)·2<sup>127</sup>. * It is equal to the hexadecimal floating-point literal * <code>0x1.fffffeP+127f</code> and also equal to * <code>Float.intBitsToFloat(0x7f7fffff)</code>. */ public static final float MAX_VALUE = 0x1.fffffeP+127f; // 3.4028235e+38f /** * A constant holding the smallest positive normal value of type * {@code float}, 2<sup>-126</sup>. It is equal to the * hexadecimal floating-point literal {@code 0x1.0p-126f} and also * equal to {@code Float.intBitsToFloat(0x00800000)}. * * @since 1.6 */ public static final float MIN_NORMAL = 0x1.0p-126f; // 1.17549435E-38f /** * A constant holding the smallest positive nonzero value of type * <code>float</code>, 2<sup>-149</sup>. It is equal to the * hexadecimal floating-point literal <code>0x0.000002P-126f</code> * and also equal to <code>Float.intBitsToFloat(0x1)</code>. */ public static final float MIN_VALUE = 0x0.000002P-126f; // 1.4e-45f /** * Maximum exponent a finite {@code float} variable may have. It * is equal to the value returned by {@code * Math.getExponent(Float.MAX_VALUE)}. * * @since 1.6 */ public static final int MAX_EXPONENT = 127; /** * Minimum exponent a normalized {@code float} variable may have. * It is equal to the value returned by {@code * Math.getExponent(Float.MIN_NORMAL)}. * * @since 1.6 */ public static final int MIN_EXPONENT = -126; /** * The number of bits used to represent a <tt>float</tt> value. * * @since 1.5 */ public static final int SIZE = 32; /** * The <code>Class</code> instance representing the primitive type * <code>float</code>. * * @since JDK1.1 */ public static final Class<Float> TYPE = Class.getPrimitiveClass("float"); /** * Returns a string representation of the <code>float</code> * argument. All characters mentioned below are ASCII characters. * <ul> * <li>If the argument is NaN, the result is the string * "<code>NaN</code>". * <li>Otherwise, the result is a string that represents the sign and * magnitude (absolute value) of the argument. If the sign is * negative, the first character of the result is * '<code>-</code>' (<code>'\u002D'</code>); if the sign is * positive, no sign character appears in the result. As for * the magnitude <i>m</i>: * <ul> * <li>If <i>m</i> is infinity, it is represented by the characters * <code>"Infinity"</code>; thus, positive infinity produces * the result <code>"Infinity"</code> and negative infinity * produces the result <code>"-Infinity"</code>. * <li>If <i>m</i> is zero, it is represented by the characters * <code>"0.0"</code>; thus, negative zero produces the result * <code>"-0.0"</code> and positive zero produces the result * <code>"0.0"</code>. * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but * less than 10<sup>7</sup>, then it is represented as the * integer part of <i>m</i>, in decimal form with no leading * zeroes, followed by '<code>.</code>' * (<code>'\u002E'</code>), followed by one or more * decimal digits representing the fractional part of * <i>m</i>. * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or * equal to 10<sup>7</sup>, then it is represented in * so-called "computerized scientific notation." Let <i>n</i> * be the unique integer such that 10<sup><i>n</i> </sup><= * <i>m</i> < 10<sup><i>n</i>+1</sup>; then let <i>a</i> * be the mathematically exact quotient of <i>m</i> and * 10<sup><i>n</i></sup> so that 1 <= <i>a</i> < 10. * The magnitude is then represented as the integer part of * <i>a</i>, as a single decimal digit, followed by * '<code>.</code>' (<code>'\u002E'</code>), followed by * decimal digits representing the fractional part of * <i>a</i>, followed by the letter '<code>E</code>' * (<code>'\u0045'</code>), followed by a representation * of <i>n</i> as a decimal integer, as produced by the * method <code>{@link * java.lang.Integer#toString(int)}</code>. * </ul> * </ul> * How many digits must be printed for the fractional part of * <i>m</i> or <i>a</i>? There must be at least one digit * to represent the fractional part, and beyond that as many, but * only as many, more digits as are needed to uniquely distinguish * the argument value from adjacent values of type * <code>float</code>. That is, suppose that <i>x</i> is the * exact mathematical value represented by the decimal * representation produced by this method for a finite nonzero * argument <i>f</i>. Then <i>f</i> must be the <code>float</code> * value nearest to <i>x</i>; or, if two <code>float</code> values are * equally close to <i>x</i>, then <i>f</i> must be one of * them and the least significant bit of the significand of * <i>f</i> must be <code>0</code>. * <p> * To create localized string representations of a floating-point * value, use subclasses of {@link java.text.NumberFormat}. * * @param f the float to be converted. * @return a string representation of the argument. */ public static String toString(float f) { return new FloatingDecimal(f).toJavaFormatString(); } /** * Returns a hexadecimal string representation of the * <code>float</code> argument. All characters mentioned below are * ASCII characters. * * <ul> * <li>If the argument is NaN, the result is the string * "<code>NaN</code>". * <li>Otherwise, the result is a string that represents the sign and * magnitude (absolute value) of the argument. If the sign is negative, * the first character of the result is '<code>-</code>' * (<code>'\u002D'</code>); if the sign is positive, no sign character * appears in the result. As for the magnitude <i>m</i>: * * <ul> * <li>If <i>m</i> is infinity, it is represented by the string * <code>"Infinity"</code>; thus, positive infinity produces the * result <code>"Infinity"</code> and negative infinity produces * the result <code>"-Infinity"</code>. * * <li>If <i>m</i> is zero, it is represented by the string * <code>"0x0.0p0"</code>; thus, negative zero produces the result * <code>"-0x0.0p0"</code> and positive zero produces the result * <code>"0x0.0p0"</code>. * * <li>If <i>m</i> is a <code>float</code> value with a * normalized representation, substrings are used to represent the * significand and exponent fields. The significand is * represented by the characters <code>"0x1."</code> * followed by a lowercase hexadecimal representation of the rest * of the significand as a fraction. Trailing zeros in the * hexadecimal representation are removed unless all the digits * are zero, in which case a single zero is used. Next, the * exponent is represented by <code>"p"</code> followed * by a decimal string of the unbiased exponent as if produced by * a call to {@link Integer#toString(int) Integer.toString} on the * exponent value. * * <li>If <i>m</i> is a <code>float</code> value with a subnormal * representation, the significand is represented by the * characters <code>"0x0."</code> followed by a * hexadecimal representation of the rest of the significand as a * fraction. Trailing zeros in the hexadecimal representation are * removed. Next, the exponent is represented by * <code>"p-126"</code>. Note that there must be at * least one nonzero digit in a subnormal significand. * * </ul> * * </ul> * * <table border> * <caption><h3>Examples</h3></caption> * <tr><th>Floating-point Value</th><th>Hexadecimal String</th> * <tr><td><code>1.0</code></td> <td><code>0x1.0p0</code></td> * <tr><td><code>-1.0</code></td> <td><code>-0x1.0p0</code></td> * <tr><td><code>2.0</code></td> <td><code>0x1.0p1</code></td> * <tr><td><code>3.0</code></td> <td><code>0x1.8p1</code></td> * <tr><td><code>0.5</code></td> <td><code>0x1.0p-1</code></td> * <tr><td><code>0.25</code></td> <td><code>0x1.0p-2</code></td> * <tr><td><code>Float.MAX_VALUE</code></td> * <td><code>0x1.fffffep127</code></td> * <tr><td><code>Minimum Normal Value</code></td> * <td><code>0x1.0p-126</code></td> * <tr><td><code>Maximum Subnormal Value</code></td> * <td><code>0x0.fffffep-126</code></td> * <tr><td><code>Float.MIN_VALUE</code></td> * <td><code>0x0.000002p-126</code></td> * </table> * @param f the <code>float</code> to be converted. * @return a hex string representation of the argument. * @since 1.5 * @author Joseph D. Darcy */ public static String toHexString(float f) { if (Math.abs(f) < FloatConsts.MIN_NORMAL && f != 0.0f ) {// float subnormal // Adjust exponent to create subnormal double, then // replace subnormal double exponent with subnormal float // exponent String s = Double.toHexString(FpUtils.scalb((double)f, /* -1022+126 */ DoubleConsts.MIN_EXPONENT- FloatConsts.MIN_EXPONENT)); return s.replaceFirst("p-1022$", "p-126"); } else // double string will be the same as float string return Double.toHexString(f); } /** * Returns a <code>Float</code> object holding the * <code>float</code> value represented by the argument string * <code>s</code>. * * <p>If <code>s</code> is <code>null</code>, then a * <code>NullPointerException</code> is thrown. * * <p>Leading and trailing whitespace characters in <code>s</code> * are ignored. Whitespace is removed as if by the {@link * String#trim} method; that is, both ASCII space and control * characters are removed. The rest of <code>s</code> should * constitute a <i>FloatValue</i> as described by the lexical * syntax rules: * * <blockquote> * <dl> * <dt><i>FloatValue:</i> * <dd><i>Sign<sub>opt</sub></i> <code>NaN</code> * <dd><i>Sign<sub>opt</sub></i> <code>Infinity</code> * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i> * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i> * <dd><i>SignedInteger</i> * </dl> * * <p> * * <dl> * <dt><i>HexFloatingPointLiteral</i>: * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i> * </dl> * * <p> * * <dl> * <dt><i>HexSignificand:</i> * <dd><i>HexNumeral</i> * <dd><i>HexNumeral</i> <code>.</code> * <dd><code>0x</code> <i>HexDigits<sub>opt</sub> * </i><code>.</code><i> HexDigits</i> * <dd><code>0X</code><i> HexDigits<sub>opt</sub> * </i><code>.</code> <i>HexDigits</i> * </dl> * * <p> * * <dl> * <dt><i>BinaryExponent:</i> * <dd><i>BinaryExponentIndicator SignedInteger</i> * </dl> * * <p> * * <dl> * <dt><i>BinaryExponentIndicator:</i> * <dd><code>p</code> * <dd><code>P</code> * </dl> * * </blockquote> * * where <i>Sign</i>, <i>FloatingPointLiteral</i>, * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and * <i>FloatTypeSuffix</i> are as defined in the lexical structure * sections of the of the <a * href="http://java.sun.com/docs/books/jls/html/">Java Language * Specification</a>. If <code>s</code> does not have the form of * a <i>FloatValue</i>, then a <code>NumberFormatException</code> * is thrown. Otherwise, <code>s</code> is regarded as * representing an exact decimal value in the usual * "computerized scientific notation" or as an exact * hexadecimal value; this exact numerical value is then * conceptually converted to an "infinitely precise" * binary value that is then rounded to type <code>float</code> * by the usual round-to-nearest rule of IEEE 754 floating-point * arithmetic, which includes preserving the sign of a zero * value. Finally, a <code>Float</code> object representing this * <code>float</code> value is returned. * * <p>To interpret localized string representations of a * floating-point value, use subclasses of {@link * java.text.NumberFormat}. * * <p>Note that trailing format specifiers, specifiers that * determine the type of a floating-point literal * (<code>1.0f</code> is a <code>float</code> value; * <code>1.0d</code> is a <code>double</code> value), do * <em>not</em> influence the results of this method. In other * words, the numerical value of the input string is converted * directly to the target floating-point type. In general, the * two-step sequence of conversions, string to <code>double</code> * followed by <code>double</code> to <code>float</code>, is * <em>not</em> equivalent to converting a string directly to * <code>float</code>. For example, if first converted to an * intermediate <code>double</code> and then to * <code>float</code>, the string<br> * <code>"1.00000017881393421514957253748434595763683319091796875001d"</code><br> * results in the <code>float</code> value * <code>1.0000002f</code>; if the string is converted directly to * <code>float</code>, <code>1.000000<b>1</b>f</code> results. * * <p>To avoid calling this method on an invalid string and having * a <code>NumberFormatException</code> be thrown, the documentation * for {@link Double#valueOf Double.valueOf} lists a regular * expression which can be used to screen the input. * * @param s the string to be parsed. * @return a <code>Float</code> object holding the value * represented by the <code>String</code> argument. * @exception NumberFormatException if the string does not contain a * parsable number. */ public static Float valueOf(String s) throws NumberFormatException { return new Float(FloatingDecimal.readJavaFormatString(s).floatValue()); } /** * Returns a <tt>Float</tt> instance representing the specified * <tt>float</tt> value. * If a new <tt>Float</tt> instance is not required, this method * should generally be used in preference to the constructor * {@link #Float(float)}, as this method is likely to yield * significantly better space and time performance by caching * frequently requested values. * * @param f a float value. * @return a <tt>Float</tt> instance representing <tt>f</tt>. * @since 1.5 */ public static Float valueOf(float f) { return new Float(f); } /** * Returns a new <code>float</code> initialized to the value * represented by the specified <code>String</code>, as performed * by the <code>valueOf</code> method of class <code>Float</code>. * * @param s the string to be parsed. * @return the <code>float</code> value represented by the string * argument. * @exception NumberFormatException if the string does not contain a * parsable <code>float</code>. * @see java.lang.Float#valueOf(String) * @since 1.2 */ public static float parseFloat(String s) throws NumberFormatException { return FloatingDecimal.readJavaFormatString(s).floatValue(); } /** * Returns <code>true</code> if the specified number is a * Not-a-Number (NaN) value, <code>false</code> otherwise. * * @param v the value to be tested. * @return <code>true</code> if the argument is NaN; * <code>false</code> otherwise. */ static public boolean isNaN(float v) { return (v != v); } /** * Returns <code>true</code> if the specified number is infinitely * large in magnitude, <code>false</code> otherwise. * * @param v the value to be tested. * @return <code>true</code> if the argument is positive infinity or * negative infinity; <code>false</code> otherwise. */ static public boolean isInfinite(float v) { return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY); } /** * The value of the Float. * * @serial */ private final float value; /** * Constructs a newly allocated <code>Float</code> object that * represents the primitive <code>float</code> argument. * * @param value the value to be represented by the <code>Float</code>. */ public Float(float value) { this.value = value; } /** * Constructs a newly allocated <code>Float</code> object that * represents the argument converted to type <code>float</code>. * * @param value the value to be represented by the <code>Float</code>. */ public Float(double value) { this.value = (float)value; } /** * Constructs a newly allocated <code>Float</code> object that * represents the floating-point value of type <code>float</code> * represented by the string. The string is converted to a * <code>float</code> value as if by the <code>valueOf</code> method. * * @param s a string to be converted to a <code>Float</code>. * @exception NumberFormatException if the string does not contain a * parsable number. * @see java.lang.Float#valueOf(java.lang.String) */ public Float(String s) throws NumberFormatException { // REMIND: this is inefficient this(valueOf(s).floatValue()); } /** * Returns <code>true</code> if this <code>Float</code> value is a * Not-a-Number (NaN), <code>false</code> otherwise. * * @return <code>true</code> if the value represented by this object is * NaN; <code>false</code> otherwise. */ public boolean isNaN() { return isNaN(value); } /** * Returns <code>true</code> if this <code>Float</code> value is * infinitely large in magnitude, <code>false</code> otherwise. * * @return <code>true</code> if the value represented by this object is * positive infinity or negative infinity; * <code>false</code> otherwise. */ public boolean isInfinite() { return isInfinite(value); } /** * Returns a string representation of this <code>Float</code> object. * The primitive <code>float</code> value represented by this object * is converted to a <code>String</code> exactly as if by the method * <code>toString</code> of one argument. * * @return a <code>String</code> representation of this object. * @see java.lang.Float#toString(float) */ public String toString() { return String.valueOf(value); } /** * Returns the value of this <code>Float</code> as a * <code>byte</code> (by casting to a <code>byte</code>). * * @return the <code>float</code> value represented by this object * converted to type <code>byte</code> */ public byte byteValue() { return (byte)value; } /** * Returns the value of this <code>Float</code> as a * <code>short</code> (by casting to a <code>short</code>). * * @return the <code>float</code> value represented by this object * converted to type <code>short</code> * @since JDK1.1 */ public short shortValue() { return (short)value; } /** * Returns the value of this <code>Float</code> as an * <code>int</code> (by casting to type <code>int</code>). * * @return the <code>float</code> value represented by this object * converted to type <code>int</code> */ public int intValue() { return (int)value; } /** * Returns value of this <code>Float</code> as a <code>long</code> * (by casting to type <code>long</code>). * * @return the <code>float</code> value represented by this object * converted to type <code>long</code> */ public long longValue() { return (long)value; } /** * Returns the <code>float</code> value of this <code>Float</code> * object. * * @return the <code>float</code> value represented by this object */ public float floatValue() { return value; } /** * Returns the <code>double</code> value of this * <code>Float</code> object. * * @return the <code>float</code> value represented by this * object is converted to type <code>double</code> and the * result of the conversion is returned. */ public double doubleValue() { return (double)value; } /** * Returns a hash code for this <code>Float</code> object. The * result is the integer bit representation, exactly as produced * by the method {@link #floatToIntBits(float)}, of the primitive * <code>float</code> value represented by this <code>Float</code> * object. * * @return a hash code value for this object. */ public int hashCode() { return floatToIntBits(value); } /** * Compares this object against the specified object. The result * is <code>true</code> if and only if the argument is not * <code>null</code> and is a <code>Float</code> object that * represents a <code>float</code> with the same value as the * <code>float</code> represented by this object. For this * purpose, two <code>float</code> values are considered to be the * same if and only if the method {@link #floatToIntBits(float)} * returns the identical <code>int</code> value when applied to * each. * <p> * Note that in most cases, for two instances of class * <code>Float</code>, <code>f1</code> and <code>f2</code>, the value * of <code>f1.equals(f2)</code> is <code>true</code> if and only if * <blockquote><pre> * f1.floatValue() == f2.floatValue() * </pre></blockquote> * <p> * also has the value <code>true</code>. However, there are two exceptions: * <ul> * <li>If <code>f1</code> and <code>f2</code> both represent * <code>Float.NaN</code>, then the <code>equals</code> method returns * <code>true</code>, even though <code>Float.NaN==Float.NaN</code> * has the value <code>false</code>. * <li>If <code>f1</code> represents <code>+0.0f</code> while * <code>f2</code> represents <code>-0.0f</code>, or vice * versa, the <code>equal</code> test has the value * <code>false</code>, even though <code>0.0f==-0.0f</code> * has the value <code>true</code>. * </ul> * This definition allows hash tables to operate properly. * * @param obj the object to be compared * @return <code>true</code> if the objects are the same; * <code>false</code> otherwise. * @see java.lang.Float#floatToIntBits(float) */ public boolean equals(Object obj) { return (obj instanceof Float) && (floatToIntBits(((Float)obj).value) == floatToIntBits(value)); } /** * Returns a representation of the specified floating-point value * according to the IEEE 754 floating-point "single format" bit * layout. * <p> * Bit 31 (the bit that is selected by the mask * <code>0x80000000</code>) represents the sign of the floating-point * number. * Bits 30-23 (the bits that are selected by the mask * <code>0x7f800000</code>) represent the exponent. * Bits 22-0 (the bits that are selected by the mask * <code>0x007fffff</code>) represent the significand (sometimes called * the mantissa) of the floating-point number. * <p>If the argument is positive infinity, the result is * <code>0x7f800000</code>. * <p>If the argument is negative infinity, the result is * <code>0xff800000</code>. * <p>If the argument is NaN, the result is <code>0x7fc00000</code>. * <p> * In all cases, the result is an integer that, when given to the * {@link #intBitsToFloat(int)} method, will produce a floating-point * value the same as the argument to <code>floatToIntBits</code> * (except all NaN values are collapsed to a single * "canonical" NaN value). * * @param value a floating-point number. * @return the bits that represent the floating-point number. */ public static int floatToIntBits(float value) { int result = floatToRawIntBits(value); // Check for NaN based on values of bit fields, maximum // exponent and nonzero significand. if ( ((result & FloatConsts.EXP_BIT_MASK) == FloatConsts.EXP_BIT_MASK) && (result & FloatConsts.SIGNIF_BIT_MASK) != 0) result = 0x7fc00000; return result; } /** * Returns a representation of the specified floating-point value * according to the IEEE 754 floating-point "single format" bit * layout, preserving Not-a-Number (NaN) values. * <p> * Bit 31 (the bit that is selected by the mask * <code>0x80000000</code>) represents the sign of the floating-point * number. * Bits 30-23 (the bits that are selected by the mask * <code>0x7f800000</code>) represent the exponent. * Bits 22-0 (the bits that are selected by the mask * <code>0x007fffff</code>) represent the significand (sometimes called * the mantissa) of the floating-point number. * <p>If the argument is positive infinity, the result is * <code>0x7f800000</code>. * <p>If the argument is negative infinity, the result is * <code>0xff800000</code>. * <p> * If the argument is NaN, the result is the integer representing * the actual NaN value. Unlike the <code>floatToIntBits</code> * method, <code>floatToRawIntBits</code> does not collapse all the * bit patterns encoding a NaN to a single "canonical" * NaN value. * <p> * In all cases, the result is an integer that, when given to the * {@link #intBitsToFloat(int)} method, will produce a * floating-point value the same as the argument to * <code>floatToRawIntBits</code>. * @param value a floating-point number. * @return the bits that represent the floating-point number. * @since 1.3 */ public static native int floatToRawIntBits(float value); /** * Returns the <code>float</code> value corresponding to a given * bit representation. * The argument is considered to be a representation of a * floating-point value according to the IEEE 754 floating-point * "single format" bit layout. * <p> * If the argument is <code>0x7f800000</code>, the result is positive * infinity. * <p> * If the argument is <code>0xff800000</code>, the result is negative * infinity. * <p> * If the argument is any value in the range * <code>0x7f800001</code> through <code>0x7fffffff</code> or in * the range <code>0xff800001</code> through * <code>0xffffffff</code>, the result is a NaN. No IEEE 754 * floating-point operation provided by Java can distinguish * between two NaN values of the same type with different bit * patterns. Distinct values of NaN are only distinguishable by * use of the <code>Float.floatToRawIntBits</code> method. * <p> * In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three * values that can be computed from the argument: * <blockquote><pre> * int s = ((bits >> 31) == 0) ? 1 : -1; * int e = ((bits >> 23) & 0xff); * int m = (e == 0) ? * (bits & 0x7fffff) << 1 : * (bits & 0x7fffff) | 0x800000; * </pre></blockquote> * Then the floating-point result equals the value of the mathematical * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>. *<p> * Note that this method may not be able to return a * <code>float</code> NaN with exactly same bit pattern as the * <code>int</code> argument. IEEE 754 distinguishes between two * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The * differences between the two kinds of NaN are generally not * visible in Java. Arithmetic operations on signaling NaNs turn * them into quiet NaNs with a different, but often similar, bit * pattern. However, on some processors merely copying a * signaling NaN also performs that conversion. In particular, * copying a signaling NaN to return it to the calling method may * perform this conversion. So <code>intBitsToFloat</code> may * not be able to return a <code>float</code> with a signaling NaN * bit pattern. Consequently, for some <code>int</code> values, * <code>floatToRawIntBits(intBitsToFloat(start))</code> may * <i>not</i> equal <code>start</code>. Moreover, which * particular bit patterns represent signaling NaNs is platform * dependent; although all NaN bit patterns, quiet or signaling, * must be in the NaN range identified above. * * @param bits an integer. * @return the <code>float</code> floating-point value with the same bit * pattern. */ public static native float intBitsToFloat(int bits); /** * Compares two <code>Float</code> objects numerically. There are * two ways in which comparisons performed by this method differ * from those performed by the Java language numerical comparison * operators (<code><, <=, ==, >= ></code>) when * applied to primitive <code>float</code> values: * <ul><li> * <code>Float.NaN</code> is considered by this method to * be equal to itself and greater than all other * <code>float</code> values * (including <code>Float.POSITIVE_INFINITY</code>). * <li> * <code>0.0f</code> is considered by this method to be greater * than <code>-0.0f</code>. * </ul> * This ensures that the <i>natural ordering</i> of <tt>Float</tt> * objects imposed by this method is <i>consistent with equals</i>. * * @param anotherFloat the <code>Float</code> to be compared. * @return the value <code>0</code> if <code>anotherFloat</code> is * numerically equal to this <code>Float</code>; a value * less than <code>0</code> if this <code>Float</code> * is numerically less than <code>anotherFloat</code>; * and a value greater than <code>0</code> if this * <code>Float</code> is numerically greater than * <code>anotherFloat</code>. * * @since 1.2 * @see Comparable#compareTo(Object) */ public int compareTo(Float anotherFloat) { return Float.compare(value, anotherFloat.value); } /** * Compares the two specified <code>float</code> values. The sign * of the integer value returned is the same as that of the * integer that would be returned by the call: * <pre> * new Float(f1).compareTo(new Float(f2)) * </pre> * * @param f1 the first <code>float</code> to compare. * @param f2 the second <code>float</code> to compare. * @return the value <code>0</code> if <code>f1</code> is * numerically equal to <code>f2</code>; a value less than * <code>0</code> if <code>f1</code> is numerically less than * <code>f2</code>; and a value greater than <code>0</code> * if <code>f1</code> is numerically greater than * <code>f2</code>. * @since 1.4 */ public static int compare(float f1, float f2) { if (f1 < f2) return -1; // Neither val is NaN, thisVal is smaller if (f1 > f2) return 1; // Neither val is NaN, thisVal is larger int thisBits = Float.floatToIntBits(f1); int anotherBits = Float.floatToIntBits(f2); return (thisBits == anotherBits ? 0 : // Values are equal (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN) 1)); // (0.0, -0.0) or (NaN, !NaN) } /** use serialVersionUID from JDK 1.0.2 for interoperability */ private static final long serialVersionUID = -2671257302660747028L; }
