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 .
author: Lee Boynton author: Arthur van Hoff author: Joseph D. Darcy version: 1.109, 06/12/07 since: JDK1.0
Field Summary
final public static int
MAX_EXPONENT Maximum exponent a finite
float variable may have.
final public static float
MAX_VALUE A constant holding the largest positive finite value of type
float , (2-2-23)·2127.
final public static int
MIN_EXPONENT Minimum exponent a normalized
float variable may have.
final public static float
MIN_NORMAL A constant holding the smallest positive normal value of type
float , 2-126.
final public static float
MIN_VALUE A constant holding the smallest positive nonzero value of type
float , 2-149.
final public static float
NEGATIVE_INFINITY A constant holding the negative infinity of type
float .
final public static float
NaN A constant holding a Not-a-Number (NaN) value of type
float .
final public static float
POSITIVE_INFINITY A constant holding the positive infinity of type
float .
final public static int
SIZE The number of bits used to represent a
float value.
TYPE The
Class instance representing the primitive type
float .
Constructor Summary
public
Float(float value) Constructs a newly allocated
Float object that
represents the primitive
float argument.
public
Float(double value) Constructs a newly allocated
Float object that
represents the argument converted to type
float .
public
Float(String s) Constructs a newly allocated
Float object that
represents the floating-point value of type
float
represented by the string.
Method Summary
public byte
byteValue() Returns the value of this
Float as a
byte (by
casting to a
byte ).
public static int
compare(float f1, float f2) Compares the two specified
float values.
public int
compareTo(Float anotherFloat) Compares two
Float objects numerically.
public double
doubleValue() Returns the
double value of this
Float object.
the float value represented by this object is converted to type double and the result of the conversion is returned.
public boolean
equals(Object obj) Compares this object against the specified object.
public 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.
Bit 31 (the bit that is selected by the mask
0x80000000 ) represents the sign of the floating-point
number.
native public 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.
Bit 31 (the bit that is selected by the mask
0x80000000 ) represents the sign of the floating-point
number.
public float
floatValue() Returns the
float value of this
Float object.
public int
hashCode() Returns a hash code for this
Float object.
native public static float
intBitsToFloat(int bits) Returns the
float value corresponding to a given
bit representation.
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.
public int
intValue() Returns the value of this
Float as an
int (by
casting to type
int ).
public static boolean
isInfinite(float v) Returns
true if the specified number is infinitely
large in magnitude,
false otherwise.
Parameters: v - the value to be tested.
public boolean
isInfinite() Returns
true if this
Float value is
infinitely large in magnitude,
false otherwise.
public static boolean
isNaN(float v) Returns
true if the specified number is a
Not-a-Number (NaN) value,
false otherwise.
Parameters: v - the value to be tested.
public boolean
isNaN() Returns
true if this
Float value is a
Not-a-Number (NaN),
false otherwise.
public long
longValue() Returns value of this
Float as a
long (by
casting to type
long ).
public 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 .
Parameters: s - the string to be parsed.
public short
shortValue() Returns the value of this
Float as a
short (by
casting to a
short ).
valueOf(float f) 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(float) , as this method is likely to yield
significantly better space and time performance by caching
frequently requested values.
Parameters: f - a float value.
A constant holding the largest positive finite value of type
float , (2-2-23)·2127.
It is equal to the hexadecimal floating-point literal
0x1.fffffeP+127f and also equal to
Float.intBitsToFloat(0x7f7fffff) .
A constant holding the smallest positive normal value of type
float , 2-126. It is equal to the
hexadecimal floating-point literal
0x1.0p-126f and also
equal to
Float.intBitsToFloat(0x00800000) .
since: 1.6
A constant holding the smallest positive nonzero value of type
float , 2-149. It is equal to the
hexadecimal floating-point literal
0x0.000002P-126f and also equal to
Float.intBitsToFloat(0x1) .
Constructs a newly allocated
Float object that
represents the argument converted to type
float .
Parameters: value - the value to be represented by the Float .
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 aparsable number. See Also:java.lang.Float.valueOf(java.lang.String)
Returns the value of this
Float as a
byte (by
casting to a
byte ).
the float value represented by this objectconverted to type byte
compare
public static int compare(float f1, float f2)(Code)
Compares the two specified
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))
Parameters: f1 - the first float to compare. Parameters: f2 - the second float to compare. the value 0 if f1 isnumerically 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 . since: 1.4
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.
Parameters: anotherFloat - the Float to be compared. the value 0 if anotherFloat isnumerically equal to this Float ; a valueless than 0 if this Float is numerically less than anotherFloat ;and a value greater than 0 if this Float is numerically greater than anotherFloat . since: 1.2 See Also:Comparable.compareTo(Object)
Returns the
double value of this
Float object.
the float value represented by this object is converted to type double and the result of the conversion is returned.
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
Float.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.
Parameters: obj - the object to be compared true if the objects are the same; false otherwise. See Also:java.lang.Float.floatToIntBits(float)
floatToIntBits
public static int floatToIntBits(float value)(Code)
Returns a representation of the specified floating-point value
according to the IEEE 754 floating-point "single format" bit
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 .
In all cases, the result is an integer that, when given to the
Float.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).
Parameters: value - a floating-point number. the bits that represent the floating-point number.
floatToRawIntBits
native public static int floatToRawIntBits(float value)(Code)
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.
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 the integer representing
the actual NaN value. Unlike the
floatToIntBits method,
floatToRawIntBits 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
Float.intBitsToFloat(int) method, will produce a
floating-point value the same as the argument to
floatToRawIntBits .
Parameters: value - a floating-point number. the bits that represent the floating-point number. since: 1.3
Returns a hash code for this
Float object. The
result is the integer bit representation, exactly as produced
by the method
Float.floatToIntBits(float) , of the primitive
float value represented by this
Float object.
a hash code value for this object.
intBitsToFloat
native public static float intBitsToFloat(int bits)(Code)
Returns the
float value corresponding to a given
bit representation.
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 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·2e-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.
Parameters: bits - an integer. the float floating-point value with the same bitpattern.
Returns
true if the specified number is infinitely
large in magnitude,
false otherwise.
Parameters: v - the value to be tested. true if the argument is positive infinity ornegative infinity; false otherwise.
Returns
true if this
Float value is
infinitely large in magnitude,
false otherwise.
true if the value represented by this object ispositive infinity or negative infinity; false otherwise.
Returns
true if the specified number is a
Not-a-Number (NaN) value,
false otherwise.
Parameters: v - the value to be tested. true if the argument is NaN; false otherwise.
Returns a new
float initialized to the value
represented by the specified
String , as performed
by the
valueOf method of class
Float .
Parameters: s - the string to be parsed. the float value represented by the stringargument. throws: NumberFormatException - if the string does not contain aparsable float . See Also:java.lang.Float.valueOf(String) since: 1.2
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(int) 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.
Examples
Floating-point Value
Hexadecimal String
1.0
0x1.0p0
-1.0
-0x1.0p0
2.0
0x1.0p1
3.0
0x1.8p1
0.5
0x1.0p-1
0.25
0x1.0p-2
Float.MAX_VALUE
0x1.fffffep127
Minimum Normal Value
0x1.0p-126
Maximum Subnormal Value
0x0.fffffep-126
Float.MIN_VALUE
0x0.000002p-126
Parameters: f - the float to be converted. a hex string representation of the argument. since: 1.5 author: Joseph D. Darcy
Returns a 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 characters
"Infinity" ; thus, positive infinity produces
the result
"Infinity" and negative infinity
produces the result
"-Infinity" .
If m is zero, it is represented by the characters
"0.0" ; thus, negative zero produces the result
"-0.0" and positive zero produces the result
"0.0" .
If m is greater than or equal to 10-3 but
less than 107, then it is represented as the
integer part of m, in decimal form with no leading
zeroes, followed by '
. '
('\u002E'), followed by one or more
decimal digits representing the fractional part of
m.
If m is less than 10-3 or greater than or
equal to 107, then it is represented in
so-called "computerized scientific notation." Let n
be the unique integer such that 10n≤
m
10n+1; then let a
be the mathematically exact quotient of m and
10n so that 1 ≤ a
10.
The magnitude is then represented as the integer part of
a, as a single decimal digit, followed by
'
. ' ('\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
java.lang.Integer.toString(int) .
How many digits must be printed for the fractional part of
m or a? There must be at least one digit
to represent the fractional part, and beyond that as many, but
only as many, more digits as are needed to uniquely distinguish
the argument value from adjacent values of type
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 floating-point
value, use subclasses of
java.text.NumberFormat .
Parameters: f - the float to be converted. a string representation of the argument.
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.
a String representation of this object. See Also:java.lang.Float.toString(float)
Returns a
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:
FloatValue:
Signopt
NaN
Signopt
Infinity
Signopt FloatingPointLiteral
Signopt HexFloatingPointLiteral
SignedInteger
HexFloatingPointLiteral:
HexSignificand BinaryExponent FloatTypeSuffixopt
HexSignificand:
HexNumeral
HexNumeral
.
0x HexDigitsopt
. HexDigits
0X HexDigitsopt
. HexDigits
BinaryExponent:
BinaryExponentIndicator SignedInteger
BinaryExponentIndicator:
p
P
where Sign, FloatingPointLiteral,
HexNumeral, HexDigits, SignedInteger and
FloatTypeSuffix are as defined in the lexical structure
sections of the Java Language
Specification. If
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 round-to-nearest rule of IEEE 754 floating-point
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
floating-point value, use subclasses of
java.text.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 , 1.0000001f results.
To avoid calling this method on an invalid string and having
a
NumberFormatException be thrown, the documentation
for
Double.valueOf Double.valueOf lists a regular
expression which can be used to screen the input.
Parameters: s - the string to be parsed. a Float object holding the valuerepresented by the String argument. throws: NumberFormatException - if the string does not contain aparsable number.
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(float) , as this method is likely to yield
significantly better space and time performance by caching
frequently requested values.
Parameters: f - a float value. a Float instance representing f . since: 1.5
