
Java^{TM} 2 Platform Standard Ed. 5.0 

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java.lang.Object java.lang.Number java.lang.Float
public final class 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
.
Field Summary  

static float 
MAX_VALUE
A constant holding the largest positive finite value of type float , (22^{23})·2^{127}. 
static float 
MIN_VALUE
A constant holding the smallest positive nonzero value of type float , 2^{149}. 
static float 
NaN
A constant holding a NotaNumber (NaN) value of type float . 
static float 
NEGATIVE_INFINITY
A constant holding the negative infinity of type float . 
static float 
POSITIVE_INFINITY
A constant holding the positive infinity of type float . 
static int 
SIZE
The number of bits used to represent a float value. 
static Class<Float> 
TYPE
The Class instance representing the primitive type
float . 
Constructor Summary  

Float(double value)
Constructs a newly allocated Float object that
represents the argument converted to type float . 

Float(float value)
Constructs a newly allocated Float object that
represents the primitive float argument. 

Float(String s)
Constructs a newly allocated Float object that
represents the floatingpoint value of type float
represented by the string. 
Method Summary  

byte 
byteValue()
Returns the value of this Float as a
byte (by casting to a byte ). 
static int 
compare(float f1,
float f2)
Compares the two specified float values. 
int 
compareTo(Float anotherFloat)
Compares two Float objects numerically. 
double 
doubleValue()
Returns the double value of this
Float object. 
boolean 
equals(Object obj)
Compares this object against the specified object. 
static int 
floatToIntBits(float value)
Returns a representation of the specified floatingpoint value according to the IEEE 754 floatingpoint "single format" bit layout. 
static int 
floatToRawIntBits(float value)
Returns a representation of the specified floatingpoint value according to the IEEE 754 floatingpoint "single format" bit layout, preserving NotaNumber (NaN) values. 
float 
floatValue()
Returns the float value of this Float
object. 
int 
hashCode()
Returns a hash code for this Float object. 
static float 
intBitsToFloat(int bits)
Returns the float value corresponding to a given
bit representation. 
int 
intValue()
Returns the value of this Float as an
int (by casting to type int ). 
boolean 
isInfinite()
Returns true if this Float value is
infinitely large in magnitude, false otherwise. 
static boolean 
isInfinite(float v)
Returns true if the specified number is infinitely
large in magnitude, false otherwise. 
boolean 
isNaN()
Returns true if this Float value is a
NotaNumber (NaN), false otherwise. 
static boolean 
isNaN(float v)
Returns true if the specified number is a
NotaNumber (NaN) value, false otherwise. 
long 
longValue()
Returns value of this Float as a long
(by casting to type long ). 
static float 
parseFloat(String s)
Returns a new float initialized to the value
represented by the specified String , as performed
by the valueOf method of class Float . 
short 
shortValue()
Returns the value of this Float as a
short (by casting to a short ). 
static String 
toHexString(float f)
Returns a hexadecimal string representation of the float argument. 
String 
toString()
Returns a string representation of this Float object. 
static String 
toString(float f)
Returns a string representation of the float
argument. 
static Float 
valueOf(float f)
Returns a Float instance representing the specified float value. 
static Float 
valueOf(String s)
Returns a Float object holding the
float value represented by the argument string
s . 
Methods inherited from class java.lang.Object 

clone, finalize, getClass, notify, notifyAll, wait, wait, wait 
Field Detail 

public static final float POSITIVE_INFINITY
float
. It is equal to the value returned by
Float.intBitsToFloat(0x7f800000)
.
public static final float NEGATIVE_INFINITY
float
. It is equal to the value returned by
Float.intBitsToFloat(0xff800000)
.
public static final float NaN
float
. It is equivalent to the value returned by
Float.intBitsToFloat(0x7fc00000)
.
public static final float MAX_VALUE
float
, (22^{23})·2^{127}.
It is equal to the hexadecimal floatingpoint literal
0x1.fffffeP+127f
and also equal to
Float.intBitsToFloat(0x7f7fffff)
.
public static final float MIN_VALUE
float
, 2^{149}. It is equal to the
hexadecimal floatingpoint literal 0x0.000002P126f
and also equal to Float.intBitsToFloat(0x1)
.
public static final int SIZE
public static final Class<Float> TYPE
Class
instance representing the primitive type
float
.
Constructor Detail 

public Float(float value)
Float
object that
represents the primitive float
argument.
value
 the value to be represented by the Float
.public Float(double value)
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
Float
object that
represents the floatingpoint 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)
Method Detail 

public static String toString(float f)
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 floatingpoint
value, use subclasses of NumberFormat
.
f
 the float to be converted.
public static String toHexString(float f)
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
"p126"
. Note that there must be at
least one nonzero digit in a subnormal significand.
Floatingpoint Value  Hexadecimal String 

1.0  0x1.0p0 
1.0  0x1.0p0 
2.0  0x1.0p1 
3.0  0x1.8p1 
0.5  0x1.0p1 
0.25  0x1.0p2 
Float.MAX_VALUE 
0x1.fffffep127 
Minimum Normal Value 
0x1.0p126 
Maximum Subnormal Value 
0x0.fffffep126 
Float.MIN_VALUE 
0x0.000002p126 
f
 the float
to be converted.
public static Float valueOf(String s) throws NumberFormatException
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 of the
 FloatValue:
 Sign_{opt}
NaN
 Sign_{opt}
Infinity
 Sign_{opt} FloatingPointLiteral
 Sign_{opt} HexFloatingPointLiteral
 SignedInteger
 HexFloatingPointLiteral:
 HexSignificand BinaryExponent FloatTypeSuffix_{opt}
 HexSignificand:
 HexNumeral
 HexNumeral
.
0x
HexDigits_{opt}.
HexDigits0X
HexDigits_{opt}.
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 roundtonearest rule of IEEE 754 floatingpoint
arithmetic, which includes preserving the sign of a zero
value. Finally, a Float
object representing this
float
value is returned.
To interpret localized string representations of a
floatingpoint value, use subclasses of NumberFormat
.
Note that trailing format specifiers, specifiers that
determine the type of a floatingpoint 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 floatingpoint type. In general, the
twostep 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 a 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)
Float(float)
, as this method is likely to yield
significantly better space and time performance by caching
frequently requested values.
f
 a float value.
public static float parseFloat(String s) throws NumberFormatException
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.
NumberFormatException
 if the string does not contain a
parsable float
.valueOf(String)
public static boolean isNaN(float v)
true
if the specified number is a
NotaNumber (NaN) value, false
otherwise.
v
 the value to be tested.
true
if the argument is NaN;
false
otherwise.public static boolean isInfinite(float v)
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 boolean isNaN()
true
if this Float
value is a
NotaNumber (NaN), false
otherwise.
true
if the value represented by this object is
NaN; false
otherwise.public boolean isInfinite()
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()
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()
Float
as a
byte
(by casting to a byte
).
byteValue
in class Number
float
value represented by this object
converted to type byte
public short shortValue()
Float
as a
short
(by casting to a short
).
shortValue
in class Number
float
value represented by this object
converted to type short
public int intValue()
Float
as an
int
(by casting to type int
).
intValue
in class Number
float
value represented by this object
converted to type int
public long longValue()
Float
as a long
(by casting to type long
).
longValue
in class Number
float
value represented by this object
converted to type long
public float floatValue()
float
value of this Float
object.
floatValue
in class Number
float
value represented by this objectpublic double doubleValue()
double
value of this
Float
object.
doubleValue
in class Number
float
value represented by this
object is converted to type double
and the
result of the conversion is returned.public int hashCode()
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)
,
Hashtable
public boolean equals(Object obj)
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 compared
true
if the objects are the same;
false
otherwise.floatToIntBits(float)
public static int floatToIntBits(float value)
Bit 31 (the bit that is selected by the mask
0x80000000
) represents the sign of the floatingpoint
number.
Bits 3023 (the bits that are selected by the mask
0x7f800000
) represent the exponent.
Bits 220 (the bits that are selected by the mask
0x007fffff
) represent the significand (sometimes called
the mantissa) of the floatingpoint 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 floatingpoint
value the same as the argument to floatToIntBits
(except all NaN values are collapsed to a single
"canonical" NaN value).
value
 a floatingpoint number.
public static int floatToRawIntBits(float value)
Bit 31 (the bit that is selected by the mask
0x80000000
) represents the sign of the floatingpoint
number.
Bits 3023 (the bits that are selected by the mask
0x7f800000
) represent the exponent.
Bits 220 (the bits that are selected by the mask
0x007fffff
) represent the significand (sometimes called
the mantissa) of the floatingpoint 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, intToRawIntBits
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
floatingpoint value the same as the argument to
floatToRawIntBits
.
value
 a floatingpoint number.
public static float intBitsToFloat(int bits)
float
value corresponding to a given
bit representation.
The argument is considered to be a representation of a
floatingpoint value according to the IEEE 754 floatingpoint
"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
floatingpoint 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:
Then the floatingpoint result equals the value of the mathematical expression s·m·2^{e150}.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 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
floatingpoint value with the same bit
pattern.public int compareTo(Float anotherFloat)
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
.
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)
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
.

Java^{TM} 2 Platform Standard Ed. 5.0 

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