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java.lang.Float
public final classFloat
extends Number { public static final floatMIN_VALUE
= 1.4e45f; public static final floatMAX_VALUE
= 3.4028235e+38f; public static final floatNEGATIVE_INFINITY
= 1.0f/0.0f; public static final floatPOSITIVE_INFINITY
= 1.0f/0.0f; public static final floatNaN
= 0.0f/0.0f; publicFloat
(float value); publicFloat
(double value); publicFloat
(String s) throws NumberFormatException; public StringtoString
(); public booleanequals
(Object obj); public inthashCode
(); public intintValue
(); public longlongValue
(); public floatfloatValue
(); public doubledoubleValue
(); public static StringtoString
(float f); public static FloatvalueOf
(String s) throws NullPointerException, NumberFormatException; public booleanisNaN
(); public static booleanisNaN
(float v); public booleanisInfinite
(); public static booleanisInfinite
(float v); public static intfloatToIntBits
(float value); public static floatintBitsToFloat
(int bits); }
20.9.1 public static final float
MIN_VALUE
= 1.4e45f;
The constant value of this field is the smallest positive nonzero value of type
float
. It is equal to the value returned by Float.intBitsToFloat(0x1)
.
20.9.2 public static final float
MAX_VALUE
= 3.4028235e+38f;
The constant value of this field is the largest positive finite value of type float
. It
is equal to the value returned by Float.intBitsToFloat(0x7f7fffff)
.
20.9.3 public static final float
NEGATIVE_INFINITY
=
1.0f/0.0f;
The constant value of this field is the negative infinity of type float
. It is equal to
the value returned by Float.intBitsToFloat(0xff800000)
.
20.9.4 public static final float
POSITIVE_INFINITY
=
1.0f/0.0f;
The constant value of this field is the positive infinity of type float
. It is equal to
the value returned by Float.intBitsToFloat(0x7f800000)
.
20.9.5 public static final float
NaN
= 0.0f/0.0f;
The constant value of this field is the NotaNumber value of type float
. It is
equal to the value returned by Float.intBitsToFloat(0x7fc00000)
.
20.9.6 public
Float
(float value)
This constructor initializes a newly created Float
object so that it represents the
primitive value that is the argument.
20.9.7 public
Float
(double value)
This constructor initializes a newly created Float
object so that it represents the
result of narrowing (§5.1.3) the argument from type double
to type float
.
20.9.8 public
Float
(String s) throws NumberFormatException
This constructor initializes a newly created Float
object so that it represents the
floatingpoint value of type float
represented by the string. The string is converted
to a float
value in exactly the manner used by the valueOf
method
(§20.9.17).
20.9.9 public String
toString
()
The primitive float
value represented by this Float
object is converted to a
string exactly as if by the method toString
of one argument (§20.9.16).
Overrides the toString
method of Object
(§20.1.2).
20.9.10 public boolean
equals
(Object obj)
The result is true
if and only if the argument is not null
and is a Float
object
that represents the same float
value as this Float
object. For this purpose, two
float
values are considered to be the same if and only if the method
floatToIntBits
(§20.9.22) returns the same int
value when applied to each.
Note that even though the ==
operator returns false
if both operands are NaN,
this equals
method will return true
if this Float
object and the argument are
both Float
objects that represent NaN. On the other hand, even though the ==
operator returns true
if one operand is positive zero and the other is negative
zero, this equals
method will return false
if this Float
object and the argument
represent zeroes of different sign. This definition allows hashtables to operate
properly.
Overrides the equals
method of Object
(§20.1.3).
20.9.11 public int
hashCode
()
The result is the integer bit representation, exactly as produced by the method
floatToIntBits
(§20.9.22), of the primitive float
value represented by this
Float
object.
Overrides the hashCode
method of Object
(§20.1.4).
20.9.12 public int
intValue
()
The float
value represented by this Float
object is converted (§5.1.3) to type
int
and the result of the conversion is returned.
Overrides the intValue
method of Number
(§20.6.1).
20.9.13 public long
longValue
()
The float
value represented by this Float
object is converted (§5.1.3) to type
long
and the result of the conversion is returned.
Overrides the longValue
method of Number
(§20.6.2).
20.9.14 public float
floatValue
()
The float
value represented by this Float
object is returned.
Overrides the floatValue
method of Number
(§20.6.3).
20.9.15 public double
doubleValue
()
The float
value represented by this Float
object is converted (§5.1.2) to type
double
and the result of the conversion is returned.
Overrides the doubleValue
method of Number
(§20.6.4).
20.9.16 public static String
toString
(float f)
The argument is converted to a readable string format as follows. All characters and characters in strings 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
of one argument (§20.7.12).
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
.
[This specification for the method toString
is scheduled for introduction in Java version 1.1. In previous versions of Java, this method produces Inf
instead of Infinity
for infinite values. Also, it renders finite values in the same form as the %g
format of the printf
function in the C programming language, which can lose precision because it produces at most six digits after the decimal point.]
20.9.17 public static Float
valueOf
(String s)
throws NullPointerException, NumberFormatException
The string s
is interpreted as the representation of a floatingpoint value and a
Float
object representing that value is created and returned.
If s
is null
, then a NullPointerException
is thrown.
Leading and trailing whitespace (§20.5.19) characters in s
are ignored. The rest of s
should constitute a FloatValue as described by the lexical syntax rules:
FloatValue:where Sign, Digits, and ExponentPart are as defined in §3.10.2. If it does not have the form of a FloatValue, then a
Sign_{opt}Digits
.
Digits_{opt}ExponentPart_{opt } Sign_{opt}
.
DigitsExponentPart_{opt }
NumberFormatException
is thrown. Otherwise,
it is regarded as representing an exact decimal value in the usual "computerized
scientific notation"; this exact decimal 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. Finally, a new object
of class Float
is created to represent this float
value.
Note that neither F
nor f
is permitted to appear in s
as a type indicator, as would be permitted in Java source code (§3.10.1).
20.9.18 public boolean
isNaN
()
The result is true
if and only if the value represented by this Float
object is
NaN.
20.9.19 public static boolean
isNaN
(float v)
The result is true
if and only if the value of the argument is NaN.
20.9.20 public boolean
isInfinite
()
The result is true
if and only if the value represented by this Float
object is positive
infinity or negative infinity.
20.9.21 public static boolean
isInfinite
(float v)
The result is true
if and only if the value of the argument is positive infinity or
negative infinity.
20.9.22 public static int
floatToIntBits
(float value)
The result is a representation of the floatingpoint argument according to the IEEE 754 floatingpoint "single format" bit layout:
0x80000000
) represents the sign of the floatingpoint number.
0x7f800000
) represent the exponent.
0x007fffff
) represent the significand (sometimes called the mantissa) of the floatingpoint number.
0x7f800000
.
0xff800000
.
0x7fc00000
.
intBitsToFloat
method (§20.9.23), will produce a floatingpoint value equal to the argument to floatToIntBits
.20.9.23 public static float
intBitsToFloat
(int bits)
The argument is considered to be a representation of a floatingpoint value according to the IEEE 754 floatingpoint "single format" bit layout. That floatingpoint value is returned as the result.
0x7f800000
, the result will be positive infinity.
0xff800000
, the result will be negative infinity.
0x7f800001
through 0x7fffffff
or in the range 0xff800001
through 0xffffffff
, the result will be NaN. (All IEEE 754 NaN values are, in effect, lumped together by the Java language into a single value called NaN.)
int s = ((bits >> 31) == 0) ? 1 : 1; int e = ((bits >> 23) & 0xff); int m = (e == 0) ? (bits & 0x7fffff) << 1 : (bits & 0x7fffff)  0x800000;Then the floatingpoint result equals the value of the mathematical expression .
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Java Language Specification (HTML generated by Suzette Pelouch on February 24, 1998)
Copyright © 1996 Sun Microsystems, Inc.
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Please send any comments or corrections to doug.kramer@sun.com