- java.lang.Object
-
- java.lang.Number
-
- java.lang.Float
-
- All Implemented Interfaces:
- Serializable, Comparable<Float>
public final class Float extends Number implements Comparable<Float>
TheFloat
class wraps a value of primitive typefloat
in an object. An object of typeFloat
contains a single field whose type isfloat
.In addition, this class provides several methods for converting a
float
to aString
and aString
to afloat
, as well as other constants and methods useful when dealing with afloat
.- Since:
- JDK1.0
- See Also:
- Serialized Form
-
-
Field Summary
Fields Modifier and Type Field and Description static int
MAX_EXPONENT
Maximum exponent a finitefloat
variable may have.static float
MAX_VALUE
A constant holding the largest positive finite value of typefloat
, (2-2-23)·2127.static int
MIN_EXPONENT
Minimum exponent a normalizedfloat
variable may have.static float
MIN_NORMAL
A constant holding the smallest positive normal value of typefloat
, 2-126.static float
MIN_VALUE
A constant holding the smallest positive nonzero value of typefloat
, 2-149.static float
NaN
A constant holding a Not-a-Number (NaN) value of typefloat
.static float
NEGATIVE_INFINITY
A constant holding the negative infinity of typefloat
.static float
POSITIVE_INFINITY
A constant holding the positive infinity of typefloat
.static int
SIZE
The number of bits used to represent afloat
value.static Class<Float>
TYPE
TheClass
instance representing the primitive typefloat
.
-
Constructor Summary
Constructors Constructor and Description Float(double value)
Constructs a newly allocatedFloat
object that represents the argument converted to typefloat
.Float(float value)
Constructs a newly allocatedFloat
object that represents the primitivefloat
argument.Float(String s)
Constructs a newly allocatedFloat
object that represents the floating-point value of typefloat
represented by the string.
-
Method Summary
Methods Modifier and Type Method and Description byte
byteValue()
Returns the value of thisFloat
as abyte
(by casting to abyte
).static int
compare(float f1, float f2)
Compares the two specifiedfloat
values.int
compareTo(Float anotherFloat)
Compares twoFloat
objects numerically.double
doubleValue()
Returns thedouble
value of thisFloat
object.boolean
equals(Object obj)
Compares this object against the specified object.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.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.float
floatValue()
Returns thefloat
value of thisFloat
object.int
hashCode()
Returns a hash code for thisFloat
object.static float
intBitsToFloat(int bits)
Returns thefloat
value corresponding to a given bit representation.int
intValue()
Returns the value of thisFloat
as anint
(by casting to typeint
).boolean
isInfinite()
Returnstrue
if thisFloat
value is infinitely large in magnitude,false
otherwise.static boolean
isInfinite(float v)
Returnstrue
if the specified number is infinitely large in magnitude,false
otherwise.boolean
isNaN()
Returnstrue
if thisFloat
value is a Not-a-Number (NaN),false
otherwise.static boolean
isNaN(float v)
Returnstrue
if the specified number is a Not-a-Number (NaN) value,false
otherwise.long
longValue()
Returns value of thisFloat
as along
(by casting to typelong
).static float
parseFloat(String s)
Returns a newfloat
initialized to the value represented by the specifiedString
, as performed by thevalueOf
method of classFloat
.short
shortValue()
Returns the value of thisFloat
as ashort
(by casting to ashort
).static String
toHexString(float f)
Returns a hexadecimal string representation of thefloat
argument.String
toString()
Returns a string representation of thisFloat
object.static String
toString(float f)
Returns a string representation of thefloat
argument.static Float
valueOf(float f)
Returns aFloat
instance representing the specifiedfloat
value.static Float
valueOf(String s)
Returns aFloat
object holding thefloat
value represented by the argument strings
.
-
-
-
Field Detail
-
POSITIVE_INFINITY
public static final float POSITIVE_INFINITY
A constant holding the positive infinity of typefloat
. It is equal to the value returned byFloat.intBitsToFloat(0x7f800000)
.- See Also:
- Constant Field Values
-
NEGATIVE_INFINITY
public static final float NEGATIVE_INFINITY
A constant holding the negative infinity of typefloat
. It is equal to the value returned byFloat.intBitsToFloat(0xff800000)
.- See Also:
- Constant Field Values
-
NaN
public static final float NaN
A constant holding a Not-a-Number (NaN) value of typefloat
. It is equivalent to the value returned byFloat.intBitsToFloat(0x7fc00000)
.- See Also:
- Constant Field Values
-
MAX_VALUE
public static final float MAX_VALUE
A constant holding the largest positive finite value of typefloat
, (2-2-23)·2127. It is equal to the hexadecimal floating-point literal0x1.fffffeP+127f
and also equal toFloat.intBitsToFloat(0x7f7fffff)
.- See Also:
- Constant Field Values
-
MIN_NORMAL
public static final float MIN_NORMAL
A constant holding the smallest positive normal value of typefloat
, 2-126. It is equal to the hexadecimal floating-point literal0x1.0p-126f
and also equal toFloat.intBitsToFloat(0x00800000)
.- Since:
- 1.6
- See Also:
- Constant Field Values
-
MIN_VALUE
public static final float MIN_VALUE
A constant holding the smallest positive nonzero value of typefloat
, 2-149. It is equal to the hexadecimal floating-point literal0x0.000002P-126f
and also equal toFloat.intBitsToFloat(0x1)
.- See Also:
- Constant Field Values
-
MAX_EXPONENT
public static final int MAX_EXPONENT
Maximum exponent a finitefloat
variable may have. It is equal to the value returned byMath.getExponent(Float.MAX_VALUE)
.- Since:
- 1.6
- See Also:
- Constant Field Values
-
MIN_EXPONENT
public static final int MIN_EXPONENT
Minimum exponent a normalizedfloat
variable may have. It is equal to the value returned byMath.getExponent(Float.MIN_NORMAL)
.- Since:
- 1.6
- See Also:
- Constant Field Values
-
SIZE
public static final int SIZE
The number of bits used to represent afloat
value.- Since:
- 1.5
- See Also:
- Constant Field Values
-
-
Constructor Detail
-
Float
public Float(float value)
Constructs a newly allocatedFloat
object that represents the primitivefloat
argument.- Parameters:
value
- the value to be represented by theFloat
.
-
Float
public Float(double value)
Constructs a newly allocatedFloat
object that represents the argument converted to typefloat
.- Parameters:
value
- the value to be represented by theFloat
.
-
Float
public Float(String s) throws NumberFormatException
Constructs a newly allocatedFloat
object that represents the floating-point value of typefloat
represented by the string. The string is converted to afloat
value as if by thevalueOf
method.- Parameters:
s
- a string to be converted to aFloat
.- Throws:
NumberFormatException
- if the string does not contain a parsable number.- See Also:
valueOf(java.lang.String)
-
-
Method Detail
-
toString
public static String toString(float f)
Returns a string representation of thefloat
argument. All characters mentioned below are ASCII characters.- If the argument is NaN, the result is the string
"
NaN
". - 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
'
-
' ('\u002D'
); if the sign is positive, no sign character appears in the result. As for the magnitude m:- If m is infinity, it is represented by the characters
"Infinity"
; thus, positive infinity produces the result"Infinity"
and negative infinity produces the result"-Infinity"
. - If m is zero, it is represented by the characters
"0.0"
; thus, negative zero produces the result"-0.0"
and positive zero produces the result"0.0"
. - If m is greater than or equal to 10-3 but
less than 107, then it is represented as the
integer part of m, in decimal form with no leading
zeroes, followed by '
.
' ('\u002E'
), followed by one or more decimal digits representing the fractional part of m. - If m is less than 10-3 or greater than or
equal to 107, then it is represented in
so-called "computerized scientific notation." Let n
be the unique integer such that 10n ≤
m < 10n+1; then let a
be the mathematically exact quotient of m and
10n so that 1 ≤ a < 10.
The magnitude is then represented as the integer part of
a, as a single decimal digit, followed by
'
.
' ('\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 methodInteger.toString(int)
.
- If m is infinity, it is represented by the characters
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 thefloat
value nearest to x; or, if twofloat
values are equally close to x, then f must be one of them and the least significant bit of the significand of f must be0
.To create localized string representations of a floating-point value, use subclasses of
NumberFormat
.- Parameters:
f
- the float to be converted.- Returns:
- a string representation of the argument.
- If the argument is NaN, the result is the string
"
-
toHexString
public static String toHexString(float f)
Returns a hexadecimal string representation of thefloat
argument. All characters mentioned below are ASCII characters.- If the argument is NaN, the result is the string
"
NaN
". - 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 '
-
' ('\u002D'
); if the sign is positive, no sign character appears in the result. As for the magnitude m:- If m is infinity, it is represented by the string
"Infinity"
; thus, positive infinity produces the result"Infinity"
and negative infinity produces the result"-Infinity"
. - If m is zero, it is represented by the string
"0x0.0p0"
; thus, negative zero produces the result"-0x0.0p0"
and positive zero produces the result"0x0.0p0"
. - If m is a
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 toInteger.toString
on the exponent value. - If m is a
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.
- If m is infinity, it is represented by the string
Examples
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
- Parameters:
f
- thefloat
to be converted.- Returns:
- a hex string representation of the argument.
- Since:
- 1.5
- If the argument is NaN, the result is the string
"
-
valueOf
public static Float valueOf(String s) throws NumberFormatException
Returns aFloat
object holding thefloat
value represented by the argument strings
.If
s
isnull
, then aNullPointerException
is thrown.Leading and trailing whitespace characters in
s
are ignored. Whitespace is removed as if by theString.trim()
method; that is, both ASCII space and control characters are removed. The rest ofs
should constitute a FloatValue as described by the lexical syntax rules:- FloatValue:
- Signopt
NaN
- Signopt
Infinity
- Signopt FloatingPointLiteral
- Signopt HexFloatingPointLiteral
- SignedInteger
- Signopt
- HexFloatingPointLiteral:
- HexSignificand BinaryExponent FloatTypeSuffixopt
- HexSignificand:
- HexNumeral
- HexNumeral
.
0x
HexDigitsopt.
HexDigits0X
HexDigitsopt.
HexDigits - HexNumeral
- BinaryExponent:
- BinaryExponentIndicator SignedInteger
- BinaryExponentIndicator:
p
P
s
does not have the form of a FloatValue, then aNumberFormatException
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 typefloat
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 ofs
is large enough in magnitude (greater than or equal to (MAX_VALUE
+ulp(MAX_VALUE)
/2), rounding tofloat
will result in an infinity and if the exact value ofs
is small enough in magnitude (less than or equal toMIN_VALUE
/2), rounding to float will result in a zero. Finally, after rounding aFloat
object representing thisfloat
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 afloat
value;1.0d
is adouble
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 todouble
followed bydouble
tofloat
, is not equivalent to converting a string directly tofloat
. For example, if first converted to an intermediatedouble
and then tofloat
, the string
"1.00000017881393421514957253748434595763683319091796875001d"
results in thefloat
value1.0000002f
; if the string is converted directly tofloat
,1.0000001f
results.To avoid calling this method on an invalid string and having a
NumberFormatException
be thrown, the documentation forDouble.valueOf
lists a regular expression which can be used to screen the input.- Parameters:
s
- the string to be parsed.- Returns:
- a
Float
object holding the value represented by theString
argument. - Throws:
NumberFormatException
- if the string does not contain a parsable number.
-
valueOf
public static Float valueOf(float f)
Returns aFloat
instance representing the specifiedfloat
value. If a newFloat
instance is not required, this method should generally be used in preference to the constructorFloat(float)
, as this method is likely to yield significantly better space and time performance by caching frequently requested values.- Parameters:
f
- a float value.- Returns:
- a
Float
instance representingf
. - Since:
- 1.5
-
parseFloat
public static float parseFloat(String s) throws NumberFormatException
Returns a newfloat
initialized to the value represented by the specifiedString
, as performed by thevalueOf
method of classFloat
.- Parameters:
s
- the string to be parsed.- Returns:
- the
float
value represented by the string argument. - Throws:
NullPointerException
- if the string is nullNumberFormatException
- if the string does not contain a parsablefloat
.- Since:
- 1.2
- See Also:
valueOf(String)
-
isNaN
public static boolean isNaN(float v)
Returnstrue
if the specified number is a Not-a-Number (NaN) value,false
otherwise.- Parameters:
v
- the value to be tested.- Returns:
true
if the argument is NaN;false
otherwise.
-
isInfinite
public static boolean isInfinite(float v)
Returnstrue
if the specified number is infinitely large in magnitude,false
otherwise.- Parameters:
v
- the value to be tested.- Returns:
true
if the argument is positive infinity or negative infinity;false
otherwise.
-
isNaN
public boolean isNaN()
Returnstrue
if thisFloat
value is a Not-a-Number (NaN),false
otherwise.- Returns:
true
if the value represented by this object is NaN;false
otherwise.
-
isInfinite
public boolean isInfinite()
Returnstrue
if thisFloat
value is infinitely large in magnitude,false
otherwise.- Returns:
true
if the value represented by this object is positive infinity or negative infinity;false
otherwise.
-
toString
public String toString()
Returns a string representation of thisFloat
object. The primitivefloat
value represented by this object is converted to aString
exactly as if by the methodtoString
of one argument.- Overrides:
toString
in classObject
- Returns:
- a
String
representation of this object. - See Also:
toString(float)
-
byteValue
public byte byteValue()
Returns the value of thisFloat
as abyte
(by casting to abyte
).
-
shortValue
public short shortValue()
Returns the value of thisFloat
as ashort
(by casting to ashort
).- Overrides:
shortValue
in classNumber
- Returns:
- the
float
value represented by this object converted to typeshort
- Since:
- JDK1.1
-
intValue
public int intValue()
Returns the value of thisFloat
as anint
(by casting to typeint
).
-
longValue
public long longValue()
Returns value of thisFloat
as along
(by casting to typelong
).
-
floatValue
public float floatValue()
Returns thefloat
value of thisFloat
object.- Specified by:
floatValue
in classNumber
- Returns:
- the
float
value represented by this object
-
doubleValue
public double doubleValue()
Returns thedouble
value of thisFloat
object.- Specified by:
doubleValue
in classNumber
- Returns:
- the
float
value represented by this object is converted to typedouble
and the result of the conversion is returned.
-
hashCode
public int hashCode()
Returns a hash code for thisFloat
object. The result is the integer bit representation, exactly as produced by the methodfloatToIntBits(float)
, of the primitivefloat
value represented by thisFloat
object.- Overrides:
hashCode
in classObject
- Returns:
- a hash code value for this object.
- See Also:
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
-
equals
public boolean equals(Object obj)
Compares this object against the specified object. The result istrue
if and only if the argument is notnull
and is aFloat
object that represents afloat
with the same value as thefloat
represented by this object. For this purpose, twofloat
values are considered to be the same if and only if the methodfloatToIntBits(float)
returns the identicalint
value when applied to each.Note that in most cases, for two instances of class
Float
,f1
andf2
, the value off1.equals(f2)
istrue
if and only iff1.floatValue() == f2.floatValue()
also has the value
true
. However, there are two exceptions:- If
f1
andf2
both representFloat.NaN
, then theequals
method returnstrue
, even thoughFloat.NaN==Float.NaN
has the valuefalse
. - If
f1
represents+0.0f
whilef2
represents-0.0f
, or vice versa, theequal
test has the valuefalse
, even though0.0f==-0.0f
has the valuetrue
.
- Overrides:
equals
in classObject
- Parameters:
obj
- the object to be compared- Returns:
true
if the objects are the same;false
otherwise.- See Also:
floatToIntBits(float)
- If
-
floatToIntBits
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 mask0x7f800000
) represent the exponent. Bits 22-0 (the bits that are selected by the mask0x007fffff
) 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 tofloatToIntBits
(except all NaN values are collapsed to a single "canonical" NaN value).- Parameters:
value
- a floating-point number.- Returns:
- the bits that represent the floating-point number.
-
floatToRawIntBits
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 mask0x7f800000
) represent the exponent. Bits 22-0 (the bits that are selected by the mask0x007fffff
) 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 tofloatToRawIntBits
.- Parameters:
value
- a floating-point number.- Returns:
- the bits that represent the floating-point number.
- Since:
- 1.3
-
intBitsToFloat
public static float intBitsToFloat(int bits)
Returns thefloat
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
through0x7fffffff
or in the range0xff800001
through0xffffffff
, 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 theFloat.floatToRawIntBits
method.In all other cases, let s, e, and m be three values that can be computed from the argument:
Then the floating-point result equals the value of the mathematical expression s·m·2e-150.int s = ((bits >> 31) == 0) ? 1 : -1; int e = ((bits >> 23) & 0xff); int m = (e == 0) ? (bits & 0x7fffff) << 1 : (bits & 0x7fffff) | 0x800000;
Note that this method may not be able to return a
float
NaN with exactly same bit pattern as theint
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. SointBitsToFloat
may not be able to return afloat
with a signaling NaN bit pattern. Consequently, for someint
values,floatToRawIntBits(intBitsToFloat(start))
may not equalstart
. 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.- Parameters:
bits
- an integer.- Returns:
- the
float
floating-point value with the same bit pattern.
-
compareTo
public int compareTo(Float anotherFloat)
Compares twoFloat
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 primitivefloat
values:-
Float.NaN
is considered by this method to be equal to itself and greater than all otherfloat
values (includingFloat.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.- Specified by:
compareTo
in interfaceComparable<Float>
- Parameters:
anotherFloat
- theFloat
to be compared.- Returns:
- the value
0
ifanotherFloat
is numerically equal to thisFloat
; a value less than0
if thisFloat
is numerically less thananotherFloat
; and a value greater than0
if thisFloat
is numerically greater thananotherFloat
. - Since:
- 1.2
- See Also:
Comparable.compareTo(Object)
-
-
compare
public static int compare(float f1, float f2)
Compares the two specifiedfloat
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))
- Parameters:
f1
- the firstfloat
to compare.f2
- the secondfloat
to compare.- Returns:
- the value
0
iff1
is numerically equal tof2
; a value less than0
iff1
is numerically less thanf2
; and a value greater than0
iff1
is numerically greater thanf2
. - Since:
- 1.4
-
-
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