public final class Float extends Number implements Comparable<Float>
The Float
class wraps a value of primitive type float
in an object. An object of type Float
contains a single field whose type is float
.
In addition, this class provides several methods for converting a float
to a String
and a String
to a float
, as well as other constants and methods useful when dealing with a float
.
public static final float POSITIVE_INFINITY
A constant holding the positive infinity of type float
. It is equal to the value returned by Float.intBitsToFloat(0x7f800000)
.
public static final float NEGATIVE_INFINITY
A constant holding the negative infinity of type float
. It is equal to the value returned by Float.intBitsToFloat(0xff800000)
.
public static final float NaN
A constant holding a Not-a-Number (NaN) value of type float
. It is equivalent to the value returned by Float.intBitsToFloat(0x7fc00000)
.
public static final float MAX_VALUE
A constant holding the largest positive finite value of type float
, (2-2-23)·2127. It is equal to the hexadecimal floating-point literal 0x1.fffffeP+127f
and also equal to Float.intBitsToFloat(0x7f7fffff)
.
public static final float MIN_NORMAL
A constant holding the smallest positive normal value of type float
, 2-126. It is equal to the hexadecimal floating-point literal 0x1.0p-126f
and also equal to Float.intBitsToFloat(0x00800000)
.
public static final float MIN_VALUE
A constant holding the smallest positive nonzero value of type float
, 2-149. It is equal to the hexadecimal floating-point literal 0x0.000002P-126f
and also equal to Float.intBitsToFloat(0x1)
.
public static final int MAX_EXPONENT
Maximum exponent a finite float
variable may have. It is equal to the value returned by Math.getExponent(Float.MAX_VALUE)
.
public static final int MIN_EXPONENT
Minimum exponent a normalized float
variable may have. It is equal to the value returned by Math.getExponent(Float.MIN_NORMAL)
.
public static final int SIZE
The number of bits used to represent a float
value.
public static final int BYTES
The number of bytes used to represent a float
value.
public static final Class<Float> TYPE
The Class
instance representing the primitive type float
.
public Float(float value)
Constructs a newly allocated Float
object that represents the primitive float
argument.
value
- the value to be represented by the Float
.public Float(double value)
Constructs a newly allocated Float
object that represents the argument converted to type float
.
value
- the value to be represented by the Float
.public Float(String s) throws NumberFormatException
Constructs a newly allocated Float
object that represents the floating-point value of type float
represented by the string. The string is converted to a float
value as if by the valueOf
method.
s
- a string to be converted to a Float
.NumberFormatException
- if the string does not contain a parsable number.valueOf(java.lang.String)
public static String toString(float f)
Returns a string representation of the float
argument. All characters mentioned below are ASCII characters.
NaN
". -
' ('\u002D'
); if the sign is positive, no sign character appears in the result. As for the magnitude m: "Infinity"
; thus, positive infinity produces the result "Infinity"
and negative infinity produces the result "-Infinity"
. "0.0"
; thus, negative zero produces the result "-0.0"
and positive zero produces the result "0.0"
. .
' ('\u002E'
), followed by one or more decimal digits representing the fractional part of m. .
' ('\u002E'
), followed by decimal digits representing the fractional part of a, followed by the letter 'E
' ('\u0045'
), followed by a representation of n as a decimal integer, as produced by the method Integer.toString(int)
. 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 float
value nearest to x; or, if two 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 0
.
To create localized string representations of a floating-point value, use subclasses of NumberFormat
.
f
- the float to be converted.public static String toHexString(float f)
Returns a hexadecimal string representation of the float
argument. All characters mentioned below are ASCII characters.
NaN
". -
' ('\u002D'
); if the sign is positive, no sign character appears in the result. As for the magnitude m: "Infinity"
; thus, positive infinity produces the result "Infinity"
and negative infinity produces the result "-Infinity"
. "0x0.0p0"
; thus, negative zero produces the result "-0x0.0p0"
and positive zero produces the result "0x0.0p0"
. float
value with a normalized representation, substrings are used to represent the significand and exponent fields. The significand is represented by the characters "0x1."
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 "p"
followed by a decimal string of the unbiased exponent as if produced by a call to Integer.toString
on the exponent value. float
value with a subnormal representation, the significand is represented by the characters "0x0."
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 "p-126"
. Note that there must be at least one nonzero digit in a subnormal significand. Floating-point Value | Hexadecimal String |
---|---|
1.0 | 0x1.0p0 |
-1.0 | -0x1.0p0 |
2.0 | 0x1.0p1 |
3.0 | 0x1.8p1 |
0.5 | 0x1.0p-1 |
0.25 | 0x1.0p-2 |
Float.MAX_VALUE | 0x1.fffffep127 |
Minimum Normal Value | 0x1.0p-126 |
Maximum Subnormal Value | 0x0.fffffep-126 |
Float.MIN_VALUE | 0x0.000002p-126 |
f
- the float
to be converted.public static Float valueOf(String s) throws NumberFormatException
Returns a Float
object holding the float
value represented by the argument string s
.
If s
is null
, then a NullPointerException
is thrown.
Leading and trailing whitespace characters in s
are ignored. Whitespace is removed as if by the String.trim()
method; that is, both ASCII space and control characters are removed. The rest of s
should constitute a FloatValue as described by the lexical syntax rules:
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
- FloatValue:
- Signopt
NaN
- Signopt
Infinity
- Signopt FloatingPointLiteral
- Signopt HexFloatingPointLiteral
- SignedInteger
- HexFloatingPointLiteral:
- HexSignificand BinaryExponent FloatTypeSuffixopt
- HexSignificand:
- HexNumeral
- HexNumeral
.
0x
HexDigitsopt.
HexDigits0X
HexDigitsopt.
HexDigits
- BinaryExponent:
- BinaryExponentIndicator SignedInteger
- BinaryExponentIndicator:
p
P
s
does not have the form of a FloatValue, then a NumberFormatException
is thrown. Otherwise, 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 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 s
is large enough in magnitude (greater than or equal to (MAX_VALUE
+ ulp(MAX_VALUE)
/2), rounding to float
will result in an infinity and if the exact value of s
is small enough in magnitude (less than or equal to MIN_VALUE
/2), rounding to float will result in a zero. Finally, after rounding a Float
object representing this float
value is returned. To interpret localized string representations of a floating-point value, use subclasses of NumberFormat
.
Note that trailing format specifiers, specifiers that determine the type of a floating-point literal (1.0f
is a float
value; 1.0d
is a 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 double
followed by double
to float
, is not equivalent to converting a string directly to float
. For example, if first converted to an intermediate double
and then to float
, the string
"1.00000017881393421514957253748434595763683319091796875001d"
results in the float
value 1.0000002f
; if the string is converted directly to float
, 1.0000001f
results.
To avoid calling this method on an invalid string and having a NumberFormatException
be thrown, the documentation for Double.valueOf
lists a regular expression which can be used to screen the input.
s
- the string to be parsed.Float
object holding the value represented by the String
argument.NumberFormatException
- if the string does not contain a parsable number.public static Float valueOf(float f)
Returns a Float
instance representing the specified float
value. If a new Float
instance is not required, this method should generally be used in preference to the constructor Float(float)
, as this method is likely to yield significantly better space and time performance by caching frequently requested values.
f
- a float value.Float
instance representing f
.public static float parseFloat(String s) throws NumberFormatException
Returns a new float
initialized to the value represented by the specified String
, as performed by the valueOf
method of class Float
.
s
- the string to be parsed.float
value represented by the string argument.NullPointerException
- if the string is nullNumberFormatException
- if the string does not contain a parsable float
.valueOf(String)
public static boolean isNaN(float v)
Returns true
if the specified number is a Not-a-Number (NaN) value, false
otherwise.
v
- the value to be tested.true
if the argument is NaN; false
otherwise.public static boolean isInfinite(float v)
Returns true
if the specified number is infinitely large in magnitude, false
otherwise.
v
- the value to be tested.true
if the argument is positive infinity or negative infinity; false
otherwise.public static boolean isFinite(float f)
Returns true
if the argument is a finite floating-point value; returns false
otherwise (for NaN and infinity arguments).
f
- the float
value to be testedtrue
if the argument is a finite floating-point value, false
otherwise.public boolean isNaN()
Returns true
if this Float
value is a Not-a-Number (NaN), false
otherwise.
true
if the value represented by this object is NaN; false
otherwise.public boolean isInfinite()
Returns true
if this Float
value is infinitely large in magnitude, false
otherwise.
true
if the value represented by this object is positive infinity or negative infinity; false
otherwise.public String toString()
Returns a string representation of this Float
object. The primitive float
value represented by this object is converted to a String
exactly as if by the method toString
of one argument.
toString
in class Object
String
representation of this object.toString(float)
public byte byteValue()
Returns the value of this Float
as a byte
after a narrowing primitive conversion.
byteValue
in class Number
float
value represented by this object converted to type byte
public short shortValue()
Returns the value of this Float
as a short
after a narrowing primitive conversion.
shortValue
in class Number
float
value represented by this object converted to type short
public int intValue()
Returns the value of this Float
as an int
after a narrowing primitive conversion.
intValue
in class Number
float
value represented by this object converted to type int
public long longValue()
Returns value of this Float
as a long
after a narrowing primitive conversion.
longValue
in class Number
float
value represented by this object converted to type long
public float floatValue()
Returns the float
value of this Float
object.
floatValue
in class Number
float
value represented by this objectpublic double doubleValue()
Returns the value of this Float
as a double
after a widening primitive conversion.
doubleValue
in class Number
float
value represented by this object converted to type double
public int hashCode()
Returns a hash code for this Float
object. The result is the integer bit representation, exactly as produced by the method floatToIntBits(float)
, of the primitive float
value represented by this Float
object.
hashCode
in class Object
Object.equals(java.lang.Object)
, System.identityHashCode(java.lang.Object)
public static int hashCode(float value)
Returns a hash code for a float
value; compatible with Float.hashCode()
.
value
- the value to hashfloat
value.public boolean equals(Object obj)
Compares this object against the specified object. The result is true
if and only if the argument is not null
and is a Float
object that represents a float
with the same value as the float
represented by this object. For this purpose, two float
values are considered to be the same if and only if the method floatToIntBits(float)
returns the identical int
value when applied to each.
Note that in most cases, for two instances of class Float
, f1
and f2
, the value of f1.equals(f2)
is true
if and only if
f1.floatValue() == f2.floatValue()
also has the value true
. However, there are two exceptions:
f1
and f2
both represent Float.NaN
, then the equals
method returns true
, even though Float.NaN==Float.NaN
has the value false
. f1
represents +0.0f
while f2
represents -0.0f
, or vice versa, the equal
test has the value false
, even though 0.0f==-0.0f
has the value true
. equals
in class Object
obj
- the object to be comparedtrue
if the objects are the same; false
otherwise.floatToIntBits(float)
public static int floatToIntBits(float 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 0x80000000
) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask 0x7f800000
) represent the exponent. Bits 22-0 (the bits that are selected by the mask 0x007fffff
) represent the significand (sometimes called the mantissa) of the floating-point number.
If the argument is positive infinity, the result is 0x7f800000
.
If the argument is negative infinity, the result is 0xff800000
.
If the argument is NaN, the result is 0x7fc00000
.
In all cases, the result is an integer that, when given to the intBitsToFloat(int)
method, will produce a floating-point value the same as the argument to floatToIntBits
(except all NaN values are collapsed to a single "canonical" NaN value).
value
- a floating-point number.public static int floatToRawIntBits(float value)
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 0x80000000
) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask 0x7f800000
) represent the exponent. Bits 22-0 (the bits that are selected by the mask 0x007fffff
) represent the significand (sometimes called the mantissa) of the floating-point number.
If the argument is positive infinity, the result is 0x7f800000
.
If the argument is negative infinity, the result is 0xff800000
.
If the argument is NaN, the result is the integer representing the actual NaN value. Unlike the floatToIntBits
method, 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 intBitsToFloat(int)
method, will produce a floating-point value the same as the argument to floatToRawIntBits
.
value
- a floating-point number.public static float intBitsToFloat(int bits)
Returns the 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 0x7f800000
, the result is positive infinity.
If the argument is 0xff800000
, the result is negative infinity.
If the argument is any value in the range 0x7f800001
through 0x7fffffff
or in the range 0xff800001
through 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 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 float
NaN with exactly same bit pattern as the 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 intBitsToFloat
may not be able to return a float
with a signaling NaN bit pattern. Consequently, for some int
values, floatToRawIntBits(intBitsToFloat(start))
may not equal 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.
bits
- an integer.float
floating-point value with the same bit pattern.public int compareTo(Float anotherFloat)
Compares two 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 (<, <=, ==, >=, >
) when applied to primitive float
values:
Float.NaN
is considered by this method to be equal to itself and greater than all other float
values (including Float.POSITIVE_INFINITY
). 0.0f
is considered by this method to be greater than -0.0f
. Float
objects imposed by this method is consistent with equals. compareTo
in interface Comparable<Float>
anotherFloat
- the Float
to be compared.0
if anotherFloat
is numerically equal to this Float
; a value less than 0
if this Float
is numerically less than anotherFloat
; and a value greater than 0
if this Float
is numerically greater than anotherFloat
.Comparable.compareTo(Object)
public static int compare(float f1, float f2)
Compares the two specified 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))
f1
- the first float
to compare.f2
- the second float
to compare.0
if f1
is numerically equal to f2
; a value less than 0
if f1
is numerically less than f2
; and a value greater than 0
if f1
is numerically greater than f2
.public static float sum(float a, float b)
Adds two float
values together as per the + operator.
a
- the first operandb
- the second operanda
and b
BinaryOperator
public static float max(float a, float b)
Returns the greater of two float
values as if by calling Math.max
.
a
- the first operandb
- the second operanda
and b
BinaryOperator
public static float min(float a, float b)
Returns the smaller of two float
values as if by calling Math.min
.
a
- the first operandb
- the second operanda
and b
BinaryOperator
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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