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JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档
Class java.lang.Float  JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档
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Class java.lang.Float
java.lang.Object

+java.lang.Number

+java.lang.Float
 public final class Float
 extends Number
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
.

MAX_VALUE
 The largest positive value of type
float
.

MIN_VALUE
 The smallest positive value of type
float
.

NaN

The NaN value of type
float
.

NEGATIVE_INFINITY
 The negative infinity of type
float
.

POSITIVE_INFINITY
 The positive infinity of type
float
.

TYPE
 The Class object representing the primitive type float.

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

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

Float(String)
 Constructs a newly allocated
Float
object that
represents the floating point value of type float
represented by the string.

byteValue()
 Returns the value of this Float as a byte (by casting to a byte).

doubleValue()
 Returns the double value of this Float.

equals(Object)
 Compares this object against some other object.

floatToIntBits(float)
 Returns the bit represention of a singlefloat value.

floatValue()
 Returns the float value of this Float object.

hashCode()
 Returns a hashcode for this Float.

intBitsToFloat(int)
 Returns the singlefloat corresponding to a given bit represention.

intValue()
 Returns the integer value of this Float (by casting to an int).

isInfinite()
 Returns true if this Float value is infinitely large in magnitude.

isInfinite(float)
 Returns true if the specified number is infinitely large in magnitude.

isNaN()
 Returns true if this Float value is NotaNumber (NaN).

isNaN(float)
 Returns true if the specified number is the special NotaNumber (NaN)
value.

longValue()
 Returns the long value of this Float (by casting to a long).

shortValue()
 Returns the value of this Float as a short (by casting to a short).

toString()
 Returns a String representation of this Float object.

toString(float)
 Returns a String representation for the specified float value.

valueOf(String)
 Returns the floating point value represented by the specified String.
POSITIVE_INFINITY
public static final float POSITIVE_INFINITY
 The positive infinity of type
float
.
NEGATIVE_INFINITY
public static final float NEGATIVE_INFINITY
 The negative infinity of type
float
.
NaN
public static final float NaN
 The NaN value of type
float
.
MAX_VALUE
public static final float MAX_VALUE
 The largest positive value of type
float
.
MIN_VALUE
public static final float MIN_VALUE
 The smallest positive value of type
float
.
TYPE
public static final Class TYPE
 The Class object representing the primitive type float.
Float
public Float(float value)
 Constructs a newly allocated
Float
object that
represents the primitive float
argument.
 Parameters:
 value  the value to be represented by the
Float
.
Float
public Float(double value)
 Constructs a newly allocated
Float
object that
represents the argument converted to type float
.
 Parameters:
 value  the value to be represented by the
Float
.
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.
 Parameters:
 s  a string to be converted to a
Float
.
 Throws: NumberFormatException
 if the string does not contain a
parsable number.
 See Also:
 valueOf
toString
public static String toString(float f)
 Returns a String representation for the specified float value.
The values NaN
, NEGATIVE_INFINITY
,
POSITIVE_INFINITY
, 0.0
, and
+0.0
are represented by the strings
"NaN"
, "Infinity"
,
"Infinity"
, "0.0"
, and
"0.0"
, respectively.
If d
is in the range
10^{3} <=
d <= 10^{7}
,
then it is converted to a String
in the style
[]ddd.ddd
. Otherwise, it is converted to a
string in the style []m.ddddE±xx
.
There is always a minimum of 1 digit after the decimal point. The
number of digits is the minimum needed to uniquely distinguish the
argument value from adjacent values of type float
.
 Parameters:
 d  the float to be converted.
 Returns:
 a string representation of the argument.
valueOf
public static Float valueOf(String s) throws NumberFormatException
 Returns the floating point value represented by the specified String.
 Parameters:
 s  the string to be parsed.
 Returns:
 a newly constructed
Float
initialized to the
value represented by the String
argument.
 Throws: NumberFormatException
 if the string does not contain a
parsable number.
isNaN
public static boolean isNaN(float v)
 Returns true if the specified number is the special NotaNumber (NaN)
value.
 Parameters:
 v  the value to be tested.
 Returns:

true
if the argument is NaN;
false
otherwise.
isInfinite
public static boolean isInfinite(float v)
 Returns true if the specified number is infinitely large in magnitude.
 Parameters:
 v  the value to be tested.
 Returns:

true
if the argument is positive infinity or
negative infinity; false
otherwise.
isNaN
public boolean isNaN()
 Returns true if this Float value is NotaNumber (NaN).
 Returns:

true
if the value represented by this object is
NaN; false
otherwise.
isInfinite
public boolean isInfinite()
 Returns true if this Float value is infinitely large in magnitude.
 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 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.
 Returns:
 a
String
representation of this object.
 Overrides:
 toString in class Object
 See Also:
 toString
byteValue
public byte byteValue()
 Returns the value of this Float as a byte (by casting to a byte).
 Overrides:
 byteValue in class Number
shortValue
public short shortValue()
 Returns the value of this Float as a short (by casting to a short).
 Overrides:
 shortValue in class Number
intValue
public int intValue()
 Returns the integer value of this Float (by casting to an int).
 Returns:
 the
float
value represented by this object
converted to type int
and the result of the
conversion is returned.
 Overrides:
 intValue in class Number
longValue
public long longValue()
 Returns the long value of this Float (by casting to a long).
 Returns:
 the
float
value represented by this object is
converted to type long
and the result of the
conversion is returned.
 Overrides:
 longValue in class Number
floatValue
public float floatValue()
 Returns the float value of this Float object.
 Returns:
 the
float
value represented by this object.
 Overrides:
 floatValue in class Number
doubleValue
public double doubleValue()
 Returns the double value of this Float.
 Overrides:
 doubleValue in class Number
hashCode
public int hashCode()
 Returns a hashcode for this Float.
 Returns:
 a hash code value for this object.
 Overrides:
 hashCode in class Object
equals
public boolean equals(Object obj)
 Compares this object against some other object.
The result is
true
if and only if the argument is
not null
and is a Float
object that
represents a float
that has the identical bit pattern
to the bit pattern of the float
represented by this
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:
 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
.
 Returns:

true
if the objects are the same;
false
otherwise.
 Overrides:
 equals in class Object
 See Also:
 floatToIntBits
floatToIntBits
public static native int floatToIntBits(float value)
 Returns the bit represention of a singlefloat value.
The result is a representation of the floatingpoint argument
according to the IEEE 754 floatingpoint "single
precision" bit layout.
Bit 31 represents the sign of the floatingpoint number. Bits
3023 represent the exponent. Bits 220 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
.
 Parameters:
 value  a floatingpoint number.
 Returns:
 the bits that represent the floatingpoint number.
intBitsToFloat
public static native float intBitsToFloat(int bits)
 Returns the singlefloat corresponding to a given bit represention.
The argument is considered to be a representation of a
floatingpoint value according to the IEEE 754 floatingpoint
"single precision" 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 0x7f8fffff
or in the range
0xff800001
through 0xff8fffff
, the result is
NaN. All IEEE 754 NaN values are, in effect, lumped together by
the Java language into a single value.
 Parameters:
 bits  an integer.
 Returns:
 the singleformat floatingpoint value with the same bit
pattern.
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