public final class Double extends Number implements Comparable<Double>
The Double
class wraps a value of the primitive type double
in an object. An object of type Double
contains a single field whose type is double
.
In addition, this class provides several methods for converting a double
to a String
and a String
to a double
, as well as other constants and methods useful when dealing with a double
.
public static final double POSITIVE_INFINITY
A constant holding the positive infinity of type double
. It is equal to the value returned by Double.longBitsToDouble(0x7ff0000000000000L)
.
public static final double NEGATIVE_INFINITY
A constant holding the negative infinity of type double
. It is equal to the value returned by Double.longBitsToDouble(0xfff0000000000000L)
.
public static final double NaN
A constant holding a Not-a-Number (NaN) value of type double
. It is equivalent to the value returned by Double.longBitsToDouble(0x7ff8000000000000L)
.
public static final double MAX_VALUE
A constant holding the largest positive finite value of type double
, (2-2-52)·21023. It is equal to the hexadecimal floating-point literal 0x1.fffffffffffffP+1023
and also equal to Double.longBitsToDouble(0x7fefffffffffffffL)
.
public static final double MIN_NORMAL
A constant holding the smallest positive normal value of type double
, 2-1022. It is equal to the hexadecimal floating-point literal 0x1.0p-1022
and also equal to Double.longBitsToDouble(0x0010000000000000L)
.
public static final double MIN_VALUE
A constant holding the smallest positive nonzero value of type double
, 2-1074. It is equal to the hexadecimal floating-point literal 0x0.0000000000001P-1022
and also equal to Double.longBitsToDouble(0x1L)
.
public static final int MAX_EXPONENT
Maximum exponent a finite double
variable may have. It is equal to the value returned by Math.getExponent(Double.MAX_VALUE)
.
public static final int MIN_EXPONENT
Minimum exponent a normalized double
variable may have. It is equal to the value returned by Math.getExponent(Double.MIN_NORMAL)
.
public static final int SIZE
The number of bits used to represent a double
value.
public static final int BYTES
The number of bytes used to represent a double
value.
public static final Class<Double> TYPE
The Class
instance representing the primitive type double
.
public Double(double value)
Constructs a newly allocated Double
object that represents the primitive double
argument.
value
- the value to be represented by the Double
.public Double(String s) throws NumberFormatException
Constructs a newly allocated Double
object that represents the floating-point value of type double
represented by the string. The string is converted to a double
value as if by the valueOf
method.
s
- a string to be converted to a Double
.NumberFormatException
- if the string does not contain a parsable number.valueOf(java.lang.String)
public static String toString(double d)
Returns a string representation of the double
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)
. double
. That is, suppose that x is the exact mathematical value represented by the decimal representation produced by this method for a finite nonzero argument d. Then d must be the double
value nearest to x; or if two double
values are equally close to x, then d must be one of them and the least significant bit of the significand of d must be 0
.
To create localized string representations of a floating-point value, use subclasses of NumberFormat
.
d
- the double
to be converted.public static String toHexString(double d)
Returns a hexadecimal string representation of the double
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"
. double
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. double
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-1022"
. 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 |
Double.MAX_VALUE | 0x1.fffffffffffffp1023 |
Minimum Normal Value | 0x1.0p-1022 |
Maximum Subnormal Value | 0x0.fffffffffffffp-1022 |
Double.MIN_VALUE | 0x0.0000000000001p-1022 |
d
- the double
to be converted.public static Double valueOf(String s) throws NumberFormatException
Returns a Double
object holding the double
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:
where Sign, FloatingPointLiteral, HexNumeral, HexDigits, SignedInteger and FloatTypeSuffix are as defined in the lexical structure sections of The Java™ Language Specification, except that underscores are not accepted between digits. If
- FloatValue:
- Signopt
NaN
- Signopt
Infinity
- Signopt FloatingPointLiteral
- Signopt HexFloatingPointLiteral
- SignedInteger
- HexFloatingPointLiteral:
- HexSignificand BinaryExponent FloatTypeSuffixopt
- HexSignificand:
- HexNumeral
- HexNumeral
.
0x
HexDigitsopt.
HexDigits0X
HexDigitsopt.
HexDigits
- BinaryExponent:
- BinaryExponentIndicator SignedInteger
- BinaryExponentIndicator:
p
P
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 double
by the usual round-to-nearest rule of IEEE 754 floating-point arithmetic, which includes preserving the sign of a zero value. Note that the round-to-nearest rule also implies overflow and underflow behaviour; if the exact value of s
is large enough in magnitude (greater than or equal to (MAX_VALUE
+ ulp(MAX_VALUE)
/2), rounding to double
will result in an infinity and if the exact value of s
is small enough in magnitude (less than or equal to MIN_VALUE
/2), rounding to float will result in a zero. Finally, after rounding a Double
object representing this double
value is returned. To interpret localized string representations of a floating-point value, use subclasses of 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. The two-step sequence of conversions, string to float
followed by float
to double
, is not equivalent to converting a string directly to double
. For example, the float
literal 0.1f
is equal to the double
value 0.10000000149011612
; the float
literal 0.1f
represents a different numerical value than the double
literal 0.1
. (The numerical value 0.1 cannot be exactly represented in a binary floating-point number.)
To avoid calling this method on an invalid string and having a NumberFormatException
be thrown, the regular expression below can be used to screen the input string:
final String Digits = "(\\p{Digit}+)"; final String HexDigits = "(\\p{XDigit}+)"; // an exponent is 'e' or 'E' followed by an optionally // signed decimal integer. final String Exp = "[eE][+-]?"+Digits; final String fpRegex = ("[\\x00-\\x20]*"+ // Optional leading "whitespace" "[+-]?(" + // Optional sign character "NaN|" + // "NaN" string "Infinity|" + // "Infinity" string // A decimal floating-point string representing a finite positive // number without a leading sign has at most five basic pieces: // Digits . Digits ExponentPart FloatTypeSuffix // // Since this method allows integer-only strings as input // in addition to strings of floating-point literals, the // two sub-patterns below are simplifications of the grammar // productions from section 3.10.2 of // The Java Language Specification. // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+ // . Digits ExponentPart_opt FloatTypeSuffix_opt "(\\.("+Digits+")("+Exp+")?)|"+ // Hexadecimal strings "((" + // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt "(0[xX]" + HexDigits + "(\\.)?)|" + // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" + ")[pP][+-]?" + Digits + "))" + "[fFdD]?))" + "[\\x00-\\x20]*");// Optional trailing "whitespace" if (Pattern.matches(fpRegex, myString)) Double.valueOf(myString); // Will not throw NumberFormatException else { // Perform suitable alternative action }
s
- the string to be parsed.Double
object holding the value represented by the String
argument.NumberFormatException
- if the string does not contain a parsable number.public static Double valueOf(double d)
Returns a Double
instance representing the specified double
value. If a new Double
instance is not required, this method should generally be used in preference to the constructor Double(double)
, as this method is likely to yield significantly better space and time performance by caching frequently requested values.
d
- a double value.Double
instance representing d
.public static double parseDouble(String s) throws NumberFormatException
Returns a new double
initialized to the value represented by the specified String
, as performed by the valueOf
method of class Double
.
s
- the string to be parsed.double
value represented by the string argument.NullPointerException
- if the string is nullNumberFormatException
- if the string does not contain a parsable double
.valueOf(String)
public static boolean isNaN(double v)
Returns true
if the specified number is a Not-a-Number (NaN) value, false
otherwise.
v
- the value to be tested.true
if the value of the argument is NaN; false
otherwise.public static boolean isInfinite(double v)
Returns true
if the specified number is infinitely large in magnitude, false
otherwise.
v
- the value to be tested.true
if the value of the argument is positive infinity or negative infinity; false
otherwise.public static boolean isFinite(double d)
Returns true
if the argument is a finite floating-point value; returns false
otherwise (for NaN and infinity arguments).
d
- the double
value to be testedtrue
if the argument is a finite floating-point value, false
otherwise.public boolean isNaN()
Returns true
if this Double
value is a Not-a-Number (NaN), false
otherwise.
true
if the value represented by this object is NaN; false
otherwise.public boolean isInfinite()
Returns true
if this Double
value is infinitely large in magnitude, false
otherwise.
true
if the value represented by this object is positive infinity or negative infinity; false
otherwise.public String toString()
Returns a string representation of this Double
object. The primitive double
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.toString(double)
public byte byteValue()
Returns the value of this Double
as a byte
after a narrowing primitive conversion.
byteValue
in class Number
double
value represented by this object converted to type byte
public short shortValue()
Returns the value of this Double
as a short
after a narrowing primitive conversion.
shortValue
in class Number
double
value represented by this object converted to type short
public int intValue()
Returns the value of this Double
as an int
after a narrowing primitive conversion.
intValue
in class Number
double
value represented by this object converted to type int
public long longValue()
Returns the value of this Double
as a long
after a narrowing primitive conversion.
longValue
in class Number
double
value represented by this object converted to type long
public float floatValue()
Returns the value of this Double
as a float
after a narrowing primitive conversion.
floatValue
in class Number
double
value represented by this object converted to type float
public double doubleValue()
Returns the double
value of this Double
object.
doubleValue
in class Number
double
value represented by this objectpublic int hashCode()
Returns a hash code for this Double
object. The result is the exclusive OR of the two halves of the long
integer bit representation, exactly as produced by the method doubleToLongBits(double)
, of the primitive double
value represented by this Double
object. That is, the hash code is the value of the expression:
(int)(v^(v>>>32))where
v
is defined by: long v = Double.doubleToLongBits(this.doubleValue());
hashCode
in class Object
hash code
value for this object.Object.equals(java.lang.Object)
, System.identityHashCode(java.lang.Object)
public static int hashCode(double value)
Returns a hash code for a double
value; compatible with Double.hashCode()
.
value
- the value to hashdouble
value.public boolean equals(Object obj)
Compares this object against the specified object. The result is true
if and only if the argument is not null
and is a Double
object that represents a double
that has the same value as the double
represented by this object. For this purpose, two double
values are considered to be the same if and only if the method doubleToLongBits(double)
returns the identical long
value when applied to each.
Note that in most cases, for two instances of class Double
, d1
and d2
, the value of d1.equals(d2)
is true
if and only if
d1.doubleValue() == d2.doubleValue()
also has the value true
. However, there are two exceptions:
d1
and d2
both represent Double.NaN
, then the equals
method returns true
, even though Double.NaN==Double.NaN
has the value false
. d1
represents +0.0
while d2
represents -0.0
, or vice versa, the equal
test has the value false
, even though +0.0==-0.0
has the value true
. equals
in class Object
obj
- the object to compare with.true
if the objects are the same; false
otherwise.doubleToLongBits(double)
public static long doubleToLongBits(double value)
Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout.
Bit 63 (the bit that is selected by the mask 0x8000000000000000L
) represents the sign of the floating-point number. Bits 62-52 (the bits that are selected by the mask 0x7ff0000000000000L
) represent the exponent. Bits 51-0 (the bits that are selected by the mask 0x000fffffffffffffL
) represent the significand (sometimes called the mantissa) of the floating-point number.
If the argument is positive infinity, the result is 0x7ff0000000000000L
.
If the argument is negative infinity, the result is 0xfff0000000000000L
.
If the argument is NaN, the result is 0x7ff8000000000000L
.
In all cases, the result is a long
integer that, when given to the longBitsToDouble(long)
method, will produce a floating-point value the same as the argument to doubleToLongBits
(except all NaN values are collapsed to a single "canonical" NaN value).
value
- a double
precision floating-point number.public static long doubleToRawLongBits(double value)
Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout, preserving Not-a-Number (NaN) values.
Bit 63 (the bit that is selected by the mask 0x8000000000000000L
) represents the sign of the floating-point number. Bits 62-52 (the bits that are selected by the mask 0x7ff0000000000000L
) represent the exponent. Bits 51-0 (the bits that are selected by the mask 0x000fffffffffffffL
) represent the significand (sometimes called the mantissa) of the floating-point number.
If the argument is positive infinity, the result is 0x7ff0000000000000L
.
If the argument is negative infinity, the result is 0xfff0000000000000L
.
If the argument is NaN, the result is the long
integer representing the actual NaN value. Unlike the doubleToLongBits
method, doubleToRawLongBits
does not collapse all the bit patterns encoding a NaN to a single "canonical" NaN value.
In all cases, the result is a long
integer that, when given to the longBitsToDouble(long)
method, will produce a floating-point value the same as the argument to doubleToRawLongBits
.
value
- a double
precision floating-point number.public static double longBitsToDouble(long bits)
Returns the double
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 "double format" bit layout.
If the argument is 0x7ff0000000000000L
, the result is positive infinity.
If the argument is 0xfff0000000000000L
, the result is negative infinity.
If the argument is any value in the range 0x7ff0000000000001L
through 0x7fffffffffffffffL
or in the range 0xfff0000000000001L
through 0xffffffffffffffffL
, 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 Double.doubleToRawLongBits
method.
In all other cases, let s, e, and m be three values that can be computed from the argument:
int s = ((bits >> 63) == 0) ? 1 : -1; int e = (int)((bits >> 52) & 0x7ffL); long m = (e == 0) ? (bits & 0xfffffffffffffL) << 1 : (bits & 0xfffffffffffffL) | 0x10000000000000L;Then the floating-point result equals the value of the mathematical expression s·m·2e-1075.
Note that this method may not be able to return a double
NaN with exactly same bit pattern as the long
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 longBitsToDouble
may not be able to return a double
with a signaling NaN bit pattern. Consequently, for some long
values, doubleToRawLongBits(longBitsToDouble(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
- any long
integer.double
floating-point value with the same bit pattern.public int compareTo(Double anotherDouble)
Compares two Double
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 double
values:
Double.NaN
is considered by this method to be equal to itself and greater than all other double
values (including Double.POSITIVE_INFINITY
). 0.0d
is considered by this method to be greater than -0.0d
. Double
objects imposed by this method is consistent with equals. compareTo
in interface Comparable<Double>
anotherDouble
- the Double
to be compared.0
if anotherDouble
is numerically equal to this Double
; a value less than 0
if this Double
is numerically less than anotherDouble
; and a value greater than 0
if this Double
is numerically greater than anotherDouble
.public static int compare(double d1, double d2)
Compares the two specified double
values. The sign of the integer value returned is the same as that of the integer that would be returned by the call:
new Double(d1).compareTo(new Double(d2))
d1
- the first double
to compared2
- the second double
to compare0
if d1
is numerically equal to d2
; a value less than 0
if d1
is numerically less than d2
; and a value greater than 0
if d1
is numerically greater than d2
.public static double sum(double a, double b)
Adds two double
values together as per the + operator.
a
- the first operandb
- the second operanda
and b
BinaryOperator
public static double max(double a, double b)
Returns the greater of two double
values as if by calling Math.max
.
a
- the first operandb
- the second operanda
and b
BinaryOperator
public static double min(double a, double b)
Returns the smaller of two double
values as if by calling Math.min
.
a
- the first operandb
- the second operanda
and b
.BinaryOperator
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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