is new.
java.lang.Objectjava.lang.Number
java.lang.Float
<
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, (2-2 -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 Not-a-Number (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 floating-point 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 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 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 represention. |
| 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 Not-a-Number (NaN), false otherwise. |
| static boolean |
isNaN
(float v) Returns true if the specified number is a Not-a-Number (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 |
Methods inherited from interface java.lang.
Comparable
|
|---|
compareTo
|
| Field Detail |
|---|
public static final float POSITIVE_INFINITY
public static final float NEGATIVE_INFINITY
public static final float NaN
public static final float MAX_VALUE
hexadecimal floating-point literal 0x1.fffffeP+127f and also equal to
public static final float MIN_VALUE
hexadecimal floating-point literal 0x0.000002P-126f and also equal to
SIZE
public static final int
SIZE
The number of bits used to represent a
float
value.
Since:
1.5
See Also:
Constant Field Values
public static final Class<
Float
> TYPE
| Constructor Detail |
|---|
public Float(float value)
public Float(double value)
public Float(String s)
throws NumberFormatException
| Method Detail |
|---|
public static String toString(float f)
To create localized string representations of a floating-point value, use subclasses of NumberFormat .
toHexString
public static
String
toHexString
(float f)
Returns a hexadecimal string representation of the float 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 to
Integer.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.
Parameters:
f - the float to be converted.
Returns:
a hex string representation of the argument.
Since:
1.5
public static Float valueOf(String s)
throws NumberFormatException
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:
- 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
.
HexDigits
0X
HexDigits
opt
.
HexDigits
BinaryExponent:
BinaryExponentIndicator SignedInteger
BinaryExponentIndicator:
p
P
,
,
HexNumeral
,
HexDigits
,
SignedInteger
and
FloatTypeSuffix
are as defined in the lexical structure sections of the of the
Java Language Specification
"computerized
notation" or as an exact hexadecimal value;
numerical
"infinitely precise"
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, 1.000000
1
f 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.
valueOf
public staticFloat
floatvalueOf
parseFloat(float f)
(Strings) throwsNumberFormatException
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 to yield significantly better space and time performance by cacheing frequently requested values.
f - a float value.
a
Float
instance representing
f
.
1.5
parseFloat
public staticfloat
booleanparseFloat
isNaN(
String
s) throws
NumberFormatException
(float v)
Returns a new float initialized to the value represented by the specified String, as performed by the valueOf method of class Float.
s
string
parsed.
the float value represented by the string argument.
Throws:
NumberFormatException
- if the string does not contain a parsable float.
Since:
1.2
See Also:
valueOf(String)
isNaN
public static booleanisNaN
isInfinite(float v)
a Not-a-Number (NaN) value,
NaN;
isInfinite
publicstatic boolean
isInfinite
isNaN(float v)
()
Returns true if the specified number is infinitely large in magnitude, false otherwise.
Parameters:
v - the value to be tested.
argument
positive infinity or negative infinity;
isNaN
public booleanisNaN
isInfinite()
a Not-a-Number (NaN),
NaN;
isInfinite
public boolean
publicStringisInfinite
toString()
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.
toString
public
String
public bytetoString
byteValue()
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
Object
a String representation of this object.
See Also:
toString(float)
byteValue
publicbyte
shortbyteValue
shortValue()
byte
byte).
byteValue
byte
shortValue
publicshort
intshortValue
intValue()
a short
a short).
Overrides:
shortValue
short
Since:
JDK1.1
intValue
publicint
longintValue
longValue()
the
value of this Float as
an int
int).
intValue
int
longValue
publiclong
floatlongValue
floatValue()
Returns value of this Float as a long (by casting to type long).
longValue
converted to type long
floatValue
publicfloat
doublefloatValue
doubleValue()
float
floatValue
doubleValue
publicdouble
intdoubleValue
hashCode()
Returns the double value of this Float object.
Specified by:
doubleValue
Number
the float value represented by this object is converted to type double and the result of the conversion is returned.
hashCode
publicint
booleanhashCode
equals()
(Objectobj)
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.
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:
hashCode
a hash code value for this object.
Object.equals(java.lang.Object)
,
Hashtable
equals
public boolean
public static intequals
floatToIntBits(
Object
obj)
(float value)
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:
If f1 and f2 both represent Float.NaN, then the equals method returns true, even though Float.NaN==Float.NaN has the value false.
If 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.
This definition allows hash tables to operate properly.
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).
Overrides:
equals
in class
Object
obj - the object to be compared
true if the objects are the same; false otherwise.
See Also:
floatToIntBits(float)
floatToIntBits
public static intfloatToIntBits
floatToRawIntBits(float value)
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.
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 floating-point value the same as the argument to
floatToIntBits (except all NaN values are collapsed to a single "canonical" NaN value).
floatToRawIntBits.
floatToRawIntBits
public staticint
floatfloatToRawIntBits
intBitsToFloat(float value)
(int bits)
the specified
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 0x7f800000, the result is positive infinity.
If the argument is
positive infinity,
0xff800000,
the result is
0x7f800000.
negative infinity.
If the argument is negative infinity, the result is 0xff800000.
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.
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 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;
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.
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.
value - a floating-point number.
the bits that represent the floating-point number.
intBitsToFloat
public static float
public intintBitsToFloat
compareTo(int bits)
(FloatanotherFloat)
Returns the float value corresponding to a given bit represention. 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
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:
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
·2
e
-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.
the float floating-point value with the same bit pattern.
public int compareTo(Float
ObjectanotherFloat)
o)
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.
This ensures that the
natural ordering
of
Float
objects imposed by this method is
consistent with equals
.
anotherFloat
Float
the value 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)
new Float(f1).compareTo(new Float(f2))