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.
float
argument. All characters 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(int)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
f the float to be converted.float argument. All characters 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".
"0x0.0p0"; thus, negative zero produces the result
"-0x0.0p0" and positive zero produces the result
"0x0.0p0".
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.
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.
| 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 |
f the float to be converted.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()s should
constitute a FloatValue as described by the lexical
syntax rules:
where Sign, FloatingPointLiteral, HexNumeral, HexDigits, SignedInteger and FloatTypeSuffix are as defined in the lexical structure sections of the Java Language Specification. If
- FloatValue:
- Signopt
NaN- Signopt
Infinity- Signopt FloatingPointLiteral
- Signopt HexFloatingPointLiteral
- SignedInteger
- HexFloatingPointLiteral:
- HexSignificand BinaryExponent FloatTypeSuffixopt
- HexSignificand:
- HexNumeral
- HexNumeral
.0xHexDigitsopt.HexDigits0XHexDigitsopt.HexDigits
- BinaryExponent:
- BinaryExponentIndicator SignedInteger
- BinaryExponentIndicator:
pP
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 lists a regular
expression which can be used to screen the input.
s the string to be parsed.Float object holding the value
represented by the String argument.NumberFormatException if the string does not contain a
parsable number.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) f a float value.Float instance representing f.float initialized to the value
represented by the specified String, as performed
by the valueOf method of class Float.
s the string to be parsed.float value represented by the string
argument.NumberFormatException if the string does not contain a
parsable float.valueOf(java.lang.String)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.
s a string to be converted to a Float.NumberFormatException if the string does not contain a
parsable number.valueOf(java.lang.String)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.
String representation of this object.toString(float)Float object. The
result is the integer bit representation, exactly as produced
by the method floatToIntBits(float)float value represented by this Float
object.
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)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.
obj the object to be comparedtrue if the objects are the same;
false otherwise.floatToIntBits(float)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
intBitsToFloat(int)floatToIntBits
(except all NaN values are collapsed to a single
"canonical" NaN value).
value a floating-point number.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
intBitsToFloat(int)floatToRawIntBits.
value a floating-point number.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;
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.float floating-point value with the same bit
pattern.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.
Float
objects imposed by this method is consistent with equals.
anotherFloat the Float to be compared.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(java.lang.Object)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))
f1 the first float to compare.f2 the second float to compare.0 if f1 is
numerically 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.