/* * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import sun.misc.FloatingDecimal; import sun.misc.FpUtils; import sun.misc.FloatConsts; import sun.misc.DoubleConsts; /** * The {@code Float} class wraps a value of primitive type * {@code float} in an object. An object of type * {@code Float} contains a single field whose type is * {@code float}. * *

In addition, this class provides several methods for converting a * {@code float} to a {@code String} and a * {@code String} to a {@code float}, as well as other * constants and methods useful when dealing with a * {@code float}. * * @author Lee Boynton * @author Arthur van Hoff * @author Joseph D. Darcy * @since JDK1.0 */ public final class Float extends Number implements Comparable { /** * A constant holding the positive infinity of type * {@code float}. It is equal to the value returned by * {@code Float.intBitsToFloat(0x7f800000)}. */ public static final float POSITIVE_INFINITY = 1.0f / 0.0f; /** * A constant holding the negative infinity of type * {@code float}. It is equal to the value returned by * {@code Float.intBitsToFloat(0xff800000)}. */ public static final float NEGATIVE_INFINITY = -1.0f / 0.0f; /** * A constant holding a Not-a-Number (NaN) value of type * {@code float}. It is equivalent to the value returned by * {@code Float.intBitsToFloat(0x7fc00000)}. */ public static final float NaN = 0.0f / 0.0f; /** * A constant holding the largest positive finite value of type * {@code float}, (2-2-23)·2127. * It is equal to the hexadecimal floating-point literal * {@code 0x1.fffffeP+127f} and also equal to * {@code Float.intBitsToFloat(0x7f7fffff)}. */ public static final float MAX_VALUE = 0x1.fffffeP+127f; // 3.4028235e+38f /** * A constant holding the smallest positive normal value of type * {@code float}, 2-126. 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}, 2-149. It is equal to the * hexadecimal floating-point literal {@code 0x0.000002P-126f} * and also equal to {@code Float.intBitsToFloat(0x1)}. */ 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 {@code float} value. * * @since 1.5 */ public static final int SIZE = 32; /** * The {@code Class} instance representing the primitive type * {@code float}. * * @since JDK1.1 */ public static final Class TYPE = Class.getPrimitiveClass("float"); /** * Returns a string representation of the {@code float} * argument. All characters mentioned below are ASCII characters. *

* How many digits must be printed for the fractional part of * m or a? 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}. That is, suppose that x is the * exact mathematical value represented by the decimal * representation produced by this method for a finite nonzero * argument f. Then f must be the {@code float} * value nearest to x; or, if two {@code float} values are * equally close to x, then f must be one of * them and the least significant bit of the significand of * f must be {@code 0}. * *

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} argument. All characters mentioned below are * ASCII characters. * *

* * * * * * * * * * * * * * * * * * *

Examples

Floating-point ValueHexadecimal String
{@code 1.0} {@code 0x1.0p0}
{@code -1.0} {@code -0x1.0p0}
{@code 2.0} {@code 0x1.0p1}
{@code 3.0} {@code 0x1.8p1}
{@code 0.5} {@code 0x1.0p-1}
{@code 0.25} {@code 0x1.0p-2}
{@code Float.MAX_VALUE}{@code 0x1.fffffep127}
{@code Minimum Normal Value}{@code 0x1.0p-126}
{@code Maximum Subnormal Value}{@code 0x0.fffffep-126}
{@code Float.MIN_VALUE}{@code 0x0.000002p-126}
* @param f the {@code float} 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} object holding the * {@code float} value represented by the argument string * {@code s}. * *

If {@code s} is {@code null}, then a * {@code NullPointerException} is thrown. * *

Leading and trailing whitespace characters in {@code s} * 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} should * constitute a FloatValue as described by the lexical * syntax rules: * *

*
*
FloatValue: *
Signopt {@code NaN} *
Signopt {@code Infinity} *
Signopt FloatingPointLiteral *
Signopt HexFloatingPointLiteral *
SignedInteger *
* *

* *

*
HexFloatingPointLiteral: *
HexSignificand BinaryExponent FloatTypeSuffixopt *
* *

* *

*
HexSignificand: *
HexNumeral *
HexNumeral {@code .} *
{@code 0x} HexDigitsopt * {@code .} HexDigits *
{@code 0X} HexDigitsopt * {@code .} HexDigits *
* *

* *

*
BinaryExponent: *
BinaryExponentIndicator SignedInteger *
* *

* *

*
BinaryExponentIndicator: *
{@code p} *
{@code P} *
* *
* * where Sign, FloatingPointLiteral, * HexNumeral, HexDigits, SignedInteger and * FloatTypeSuffix are as defined in the lexical structure * sections of * The Java™ Language Specification, * except that underscores are not accepted between digits. * If {@code s} does not have the form of * a FloatValue, then a {@code NumberFormatException} * is thrown. Otherwise, {@code s} 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} * by the usual round-to-nearest rule of IEEE 754 floating-point * arithmetic, which includes preserving the sign of a zero * value. * * Note that the round-to-nearest rule also implies overflow and * underflow behaviour; if the exact value of {@code s} is large * enough in magnitude (greater than or equal to ({@link * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2), * rounding to {@code float} will result in an infinity and if the * exact value of {@code s} is small enough in magnitude (less * than or equal to {@link #MIN_VALUE}/2), rounding to float will * result in a zero. * * Finally, after rounding a {@code Float} object representing * this {@code float} value is returned. * *

To interpret localized string representations of a * floating-point value, use subclasses of {@link * java.text.NumberFormat}. * *

Note that trailing format specifiers, specifiers that * determine the type of a floating-point literal * ({@code 1.0f} is a {@code float} value; * {@code 1.0d} is a {@code double} value), do * not 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} * followed by {@code double} to {@code float}, is * not equivalent to converting a string directly to * {@code float}. For example, if first converted to an * intermediate {@code double} and then to * {@code float}, the string
* {@code "1.00000017881393421514957253748434595763683319091796875001d"}
* results in the {@code float} value * {@code 1.0000002f}; if the string is converted directly to * {@code float}, 1.0000001f results. * *

To avoid calling this method on an invalid string and having * a {@code NumberFormatException} 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} object holding the value * represented by the {@code String} argument. * @throws 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 {@code Float} instance representing the specified * {@code float} value. * If a new {@code Float} 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 {@code Float} instance representing {@code f}. * @since 1.5 */ public static Float valueOf(float f) { return new Float(f); } /** * Returns a new {@code float} initialized to the value * represented by the specified {@code String}, as performed * by the {@code valueOf} method of class {@code Float}. * * @param s the string to be parsed. * @return the {@code float} value represented by the string * argument. * @throws NullPointerException if the string is null * @throws NumberFormatException if the string does not contain a * parsable {@code float}. * @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} if the specified number is a * Not-a-Number (NaN) value, {@code false} otherwise. * * @param v the value to be tested. * @return {@code true} if the argument is NaN; * {@code false} otherwise. */ static public boolean isNaN(float v) { return (v != v); } /** * Returns {@code true} if the specified number is infinitely * large in magnitude, {@code false} otherwise. * * @param v the value to be tested. * @return {@code true} if the argument is positive infinity or * negative infinity; {@code false} 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} object that * represents the primitive {@code float} argument. * * @param value the value to be represented by the {@code Float}. */ public Float(float value) { this.value = value; } /** * Constructs a newly allocated {@code Float} object that * represents the argument converted to type {@code float}. * * @param value the value to be represented by the {@code Float}. */ public Float(double value) { this.value = (float)value; } /** * Constructs a newly allocated {@code Float} object that * represents the floating-point value of type {@code float} * represented by the string. The string is converted to a * {@code float} value as if by the {@code valueOf} method. * * @param s a string to be converted to a {@code Float}. * @throws 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} if this {@code Float} value is a * Not-a-Number (NaN), {@code false} otherwise. * * @return {@code true} if the value represented by this object is * NaN; {@code false} otherwise. */ public boolean isNaN() { return isNaN(value); } /** * Returns {@code true} if this {@code Float} value is * infinitely large in magnitude, {@code false} otherwise. * * @return {@code true} if the value represented by this object is * positive infinity or negative infinity; * {@code false} otherwise. */ public boolean isInfinite() { return isInfinite(value); } /** * Returns a string representation of this {@code Float} object. * The primitive {@code float} value represented by this object * is converted to a {@code String} exactly as if by the method * {@code toString} of one argument. * * @return a {@code String} representation of this object. * @see java.lang.Float#toString(float) */ public String toString() { return Float.toString(value); } /** * Returns the value of this {@code Float} as a {@code byte} after * a narrowing primitive conversion. * * @return the {@code float} value represented by this object * converted to type {@code byte} * @jls 5.1.3 Narrowing Primitive Conversions */ public byte byteValue() { return (byte)value; } /** * Returns the value of this {@code Float} as a {@code short} * after a narrowing primitive conversion. * * @return the {@code float} value represented by this object * converted to type {@code short} * @jls 5.1.3 Narrowing Primitive Conversions * @since JDK1.1 */ public short shortValue() { return (short)value; } /** * Returns the value of this {@code Float} as an {@code int} after * a narrowing primitive conversion. * * @return the {@code float} value represented by this object * converted to type {@code int} * @jls 5.1.3 Narrowing Primitive Conversions */ public int intValue() { return (int)value; } /** * Returns value of this {@code Float} as a {@code long} after a * narrowing primitive conversion. * * @return the {@code float} value represented by this object * converted to type {@code long} * @jls 5.1.3 Narrowing Primitive Conversions */ public long longValue() { return (long)value; } /** * Returns the {@code float} value of this {@code Float} object. * * @return the {@code float} value represented by this object */ public float floatValue() { return value; } /** * Returns the value of this {@code Float} as a {@code double} * after a widening primitive conversion. * * @return the {@code float} value represented by this * object converted to type {@code double} * @jls 5.1.2 Widening Primitive Conversions */ public double doubleValue() { return (double)value; } /** * Returns a hash code for this {@code Float} object. The * result is the integer bit representation, exactly as produced * by the method {@link #floatToIntBits(float)}, of the primitive * {@code float} value represented by this {@code Float} * 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} if and only if the argument is not * {@code null} and is a {@code Float} object that * represents a {@code float} with the same value as the * {@code float} represented by this object. For this * purpose, two {@code float} values are considered to be the * same if and only if the method {@link #floatToIntBits(float)} * returns the identical {@code int} value when applied to * each. * *

Note that in most cases, for two instances of class * {@code Float}, {@code f1} and {@code f2}, the value * of {@code f1.equals(f2)} is {@code true} if and only if * * 

     *   f1.floatValue() == f2.floatValue()
     *
* *

also has the value {@code true}. However, there are two exceptions: *

* * This definition allows hash tables to operate properly. * * @param obj the object to be compared * @return {@code true} if the objects are the same; * {@code false} 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. * *

Bit 31 (the bit that is selected by the mask * {@code 0x80000000}) represents the sign of the floating-point * number. * Bits 30-23 (the bits that are selected by the mask * {@code 0x7f800000}) represent the exponent. * Bits 22-0 (the bits that are selected by the mask * {@code 0x007fffff}) represent the significand (sometimes called * the mantissa) of the floating-point number. * *

If the argument is positive infinity, the result is * {@code 0x7f800000}. * *

If the argument is negative infinity, the result is * {@code 0xff800000}. * *

If the argument is NaN, the result is {@code 0x7fc00000}. * *

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} * (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. * *

Bit 31 (the bit that is selected by the mask * {@code 0x80000000}) represents the sign of the floating-point * number. * Bits 30-23 (the bits that are selected by the mask * {@code 0x7f800000}) represent the exponent. * Bits 22-0 (the bits that are selected by the mask * {@code 0x007fffff}) represent the significand (sometimes called * the mantissa) of the floating-point number. * *

If the argument is positive infinity, the result is * {@code 0x7f800000}. * *

If the argument is negative infinity, the result is * {@code 0xff800000}. * *

If the argument is NaN, the result is the integer representing * the actual NaN value. Unlike the {@code floatToIntBits} * method, {@code floatToRawIntBits} does not collapse all the * bit patterns encoding a NaN to a single "canonical" * NaN value. * *

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}. * * @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} 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. * *

If the argument is {@code 0x7f800000}, the result is positive * infinity. * *

If the argument is {@code 0xff800000}, the result is negative * infinity. * *

If the argument is any value in the range * {@code 0x7f800001} through {@code 0x7fffffff} or in * the range {@code 0xff800001} through * {@code 0xffffffff}, 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} method. * *

In all other cases, let s, e, and m be three * values that can be computed from the argument: * * 

     * int s = ((bits >> 31) == 0) ? 1 : -1;
     * int e = ((bits >> 23) & 0xff);
     * int m = (e == 0) ?
     *                 (bits & 0x7fffff) << 1 :
     *                 (bits & 0x7fffff) | 0x800000;
     *
* * Then the floating-point result equals the value of the mathematical * expression s·m·2e-150. * *

Note that this method may not be able to return a * {@code float} NaN with exactly same bit pattern as the * {@code int} argument. IEEE 754 distinguishes between two * kinds of NaNs, quiet NaNs and signaling NaNs. 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} may * not be able to return a {@code float} with a signaling NaN * bit pattern. Consequently, for some {@code int} values, * {@code floatToRawIntBits(intBitsToFloat(start))} may * not equal {@code start}. 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} floating-point value with the same bit * pattern. */ public static native float intBitsToFloat(int bits); /** * Compares two {@code Float} 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 <, <=, ==, >=, >}) when * applied to primitive {@code float} values: * *

* * This ensures that the natural ordering of {@code Float} * objects imposed by this method is consistent with equals. * * @param anotherFloat the {@code Float} to be compared. * @return the value {@code 0} if {@code anotherFloat} is * numerically equal to this {@code Float}; a value * less than {@code 0} if this {@code Float} * is numerically less than {@code anotherFloat}; * and a value greater than {@code 0} if this * {@code Float} is numerically greater than * {@code anotherFloat}. * * @since 1.2 * @see Comparable#compareTo(Object) */ public int compareTo(Float anotherFloat) { return Float.compare(value, anotherFloat.value); } /** * Compares the two specified {@code float} values. The sign * of the integer value returned is the same as that of the * integer that would be returned by the call: * 
     *    new Float(f1).compareTo(new Float(f2))
     *
* * @param f1 the first {@code float} to compare. * @param f2 the second {@code float} to compare. * @return the value {@code 0} if {@code f1} is * numerically equal to {@code f2}; a value less than * {@code 0} if {@code f1} is numerically less than * {@code f2}; and a value greater than {@code 0} * if {@code f1} is numerically greater than * {@code f2}. * @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 // Cannot use floatToRawIntBits because of possibility of NaNs. 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; }