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java.lang.Object 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
The largest positive value of type float . 

static float 
MIN_VALUE
The smallest positive value of type float . 

static float 
NEGATIVE_INFINITY
The negative infinity of type float . 

static float 
NaN
The NotaNumber (NaN) value of type float . 

static float 
POSITIVE_INFINITY
The positive infinity of 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. 
Method Summary  

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

double 
doubleValue()
Returns the double value of this Float object. 

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

static int 
floatToIntBits(float value)
Returns the bit representation of a singlefloat value. 

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

int 
hashCode()
Returns a hashcode for this Float object. 

static float 
intBitsToFloat(int bits)
Returns the singlefloat corresponding to a given bit representation. 

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

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

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

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

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

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

static float 
parseFloat(String s)
Returns a new float initialized to the value represented by the specified String . 

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

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

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

static Float 
valueOf(String s)
Returns the floating point value represented by the specified String. 
Methods inherited from class java.lang.Object 

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 equal to the value returned by
Float.intBitsToFloat(0x7fc00000)
.
public static final float MAX_VALUE
float
. It is
equal to the value returned by
Float.intBitsToFloat(0x7f7fffff)
.
public static final float MIN_VALUE
float
. It
is equal to the value returned by
Float.intBitsToFloat(0x1)
.
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
.Method Detail 

public static String toString(float f)
Integer.toString(int)
of one argument.
f
 the float to be converted.
public static Float valueOf(String s) throws NumberFormatException
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 characters in s are ignored. The rest
of s
should constitute a FloatValue as described
by the lexical syntax rules:
where Sign, FloatingPointLiteral are as defined in Section 3.10.2 of the Java Language Specification. If it does not have the form of a FloatValue, then aFloatValue: Sign_{opt} FloatingPointLiteral
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.
s
 the string to be parsed.
Float
initialized to the
value represented by the String
argument.
NumberFormatException
 if the string does not contain a
parsable number.public static float parseFloat(String s) throws NumberFormatException
String
.
s
 the string to be parsed.
NumberFormatException
 if the string does not contain a
parsable float.public static boolean isNaN(float v)
v
 the value to be tested.
true
if the argument is NaN;
false
otherwise.public static boolean isInfinite(float v)
v
 the value to be tested.
true
if the argument is positive infinity or
negative infinity; false
otherwise.public boolean isNaN()
Float
value is NotaNumber (NaN).
true
if the value represented by this object is
NaN; false
otherwise.public boolean isInfinite()
true
if the value represented by this object is
positive infinity or negative infinity;
false
otherwise.public String toString()
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.Float.toString(float)
public byte byteValue()
public short shortValue()
public int intValue()
float
value represented by this object
converted to type int
and the result of the
conversion is returned.public long longValue()
float
value represented by this object is
converted to type long
and the result of the
conversion is returned.public float floatValue()
float
value represented by this object.public double doubleValue()
float
value represented by this
object is converted to type double
and the
result of the conversion is returned.public int hashCode()
Float.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
that has the identical bit pattern
to the bit pattern of the float
represented by this
object. For this purpose, two float values are considered to be
the same if and only if the method Float.floatToIntBits(float)
returns the same 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.Float.floatToIntBits(float)
public static int floatToIntBits(float value)
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
.
Float.intBitsToFloat(int)
method, will produce a floatingpoint
value equal to the argument to floatToIntBits
.
value
 a floatingpoint number.
public static float intBitsToFloat(int bits)
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
NaN. All IEEE 754 NaN values of type float
are, in effect,
lumped together by the Java programming language into a single
float
value called NaN.
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;
bits
 an integer.


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