Double (Java Platform SE 6)
Java™&PlatformStandard&Ed.&6
Class Double
java.lang.Double
All Implemented Interfaces: , &&
public final class Doubleextends implements &&
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
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
static&int
&&&&&&&&&&Maximum exponent a finite double variable may have.
static&double
&&&&&&&&&&A constant holding the largest positive finite value of type
(2-2-52)&21023.
static&int
&&&&&&&&&&Minimum exponent a normalized double variable may
static&double
&&&&&&&&&&A constant holding the smallest positive normal value of type
double, 2-1022.
static&double
&&&&&&&&&&A constant holding the smallest positive nonzero value of type
double, 2-1074.
static&double
&&&&&&&&&&A constant holding a Not-a-Number (NaN) value of type
static&double
&&&&&&&&&&A constant holding the negative infinity of type
static&double
&&&&&&&&&&A constant holding the positive infinity of type
static&int
&&&&&&&&&&The number of bits used to represent a double value.
&&&&&&&&&&The Class instance representing the primitive type
(double&value)
&&&&&&&&&&Constructs a newly allocated Double object that
represents the primitive double argument.
&&&&&&&&&&Constructs a newly allocated Double object that
represents the floating-point value of type double
represented by the string.
&&&&&&&&&&Returns the value of this Double as a byte (by
casting to a byte).
static&int
(double&d1,
double&d2)
&&&&&&&&&&Compares the two specified double values.
(&anotherDouble)
&&&&&&&&&&Compares two Double objects numerically.
static&long
(double&value)
&&&&&&&&&&Returns a representation of the specified floating-point value
according to the IEEE 754 floating-point "double
format" bit layout.
static&long
(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.
&&&&&&&&&&Returns the double value of this
Double object.
&&&&&&&&&&Compares this object against the specified object.
&&&&&&&&&&Returns the float value of this
Double object.
&&&&&&&&&&Returns a hash code for this Double object.
&&&&&&&&&&Returns the value of this Double as an
int (by casting to type int).
&&&&&&&&&&Returns true if this Double value is
infinitely large in magnitude, false otherwise.
static&boolean
(double&v)
&&&&&&&&&&Returns true if the specified number is infinitely
large in magnitude, false otherwise.
&&&&&&&&&&Returns true if this Double value is
a Not-a-Number (NaN), false otherwise.
static&boolean
(double&v)
&&&&&&&&&&Returns true if the specified number is a
Not-a-Number (NaN) value, false otherwise.
static&double
(long&bits)
&&&&&&&&&&Returns the double value corresponding to a given
bit representation.
&&&&&&&&&&Returns the value of this Double as a
long (by casting to type long).
static&double
&&&&&&&&&&Returns a new double initialized to the value
represented by the specified String, as performed
by the valueOf method of class
&&&&&&&&&&Returns the value of this Double as a
short (by casting to a short).
(double&d)
&&&&&&&&&&Returns a hexadecimal string representation of the
double argument.
&&&&&&&&&&Returns a string representation of this Double object.
(double&d)
&&&&&&&&&&Returns a string representation of the double
(double&d)
&&&&&&&&&&Returns a Double instance representing the specified
double value.
&&&&&&&&&&Returns a Double object holding the
double value represented by the argument string
, , , , , , ,
POSITIVE_INFINITY
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(0x7ff0L).
NEGATIVE_INFINITY
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(0xfff0L).
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(0x7ff0L).
public static final double MAX_VALUE
A constant holding the largest positive finite value of type
(2-2-52)&21023.
It is equal to
the hexadecimal floating-point literal
0x1.fffffffffffffP+1023 and also equal to
Double.longBitsToDouble(0x7fefffffffffffffL).
MIN_NORMAL
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(0x0000L).
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
0x0.1P-1022 and also equal to
Double.longBitsToDouble(0x1L).
MAX_EXPONENT
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).
MIN_EXPONENT
public static final int MIN_EXPONENT
Minimum exponent a normalized double variable may
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 && TYPE
The Class instance representing the primitive type
public Double(double&value)
Constructs a newly allocated Double object that
represents the primitive double argument.
Parameters:value - the value to be represented by the Double.
public Double(&s)
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.
Parameters:s - a string to be converted to a Double.
- if the string does not contain a
parsable number.See Also:
public static
toString(double&d)
Returns a string representation of the double
argument. All characters mentioned below are ASCII characters.
If the argument is NaN, the result is the string
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
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 .
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 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 .
Parameters:d - the double to be converted.
Returns:a string representation of the argument.
toHexString
public static
toHexString(double&d)
Returns a hexadecimal string representation of the
double argument. All characters mentioned below
are ASCII characters.
If the argument is NaN, the result is the string
Otherwise, the result is a string that represents the sign
and magnitude 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 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
exponent value.
If m is a 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
Trailing zeros in the hexadecimal representation are
removed. Next, the exponent is represented by
Note that there must be at
least one nonzero digit in a subnormal significand.
Floating-point ValueHexadecimal String
-1.0 -0x1.0p0
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
0x0.1p-1022
Parameters:d - the double to be converted.
Returns:a hex string representation of the argument.Since:
public static
valueOf(&s)
Returns a Double object holding the
double value represented by the argument string
If s is null, then a
NullPointerException is thrown.
Leading and trailing whitespace characters in s
are ignored.
Whitespace is removed
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:
where Sign, FloatingPointLiteral,
HexNumeral, HexDigits, SignedInteger and
FloatTypeSuffix are as defined in the lexical structure
sections of the 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
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. Finally, a Double object representing this
double value is returned.
To interpret localized string representations of a
floating-point value, use subclasses of .
Note that trailing format specifiers, specifiers that
determine the type of a floating-point literal
(1.0f is a float
1.0d is a double value), do
not influence the results of this method.
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 0.11612; 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][+-]?"+D
final String fpRegex
("[\\x00-\\x20]*"+
// Optional leading &whitespace&
"[+-]?(" + // Optional sign character
// "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 the Java Language Specification, 2nd
// edition, section 3.10.2.
// 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
// Perform suitable alternative action
Parameters:s - the string to be parsed.
Returns:a Double object holding the value
represented by the String argument.
- if the string does not contain a
parsable number.
public static
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
, as this method is likely to yield
significantly better space and time performance by caching
frequently requested values.
Parameters:d - a double value.
Returns:a Double instance representing d.Since:
parseDouble
public static double parseDouble(&s)
Returns a new double initialized to the value
represented by the specified String, as performed
by the valueOf method of class
Parameters:s - the string to be parsed.
Returns:the double value represented by the string
- if the string does not contain
a parsable double.Since:
public static boolean isNaN(double&v)
Returns true if the specified number is a
Not-a-Number (NaN) value, false otherwise.
Parameters:v - the value to be tested.
Returns:true if the value of the argument is NaN;
false otherwise.
isInfinite
public static boolean isInfinite(double&v)
Returns true if the specified number is infinitely
large in magnitude, false otherwise.
Parameters:v - the value to be tested.
Returns:true if the value of the argument is positive
false otherwise.
public boolean isNaN()
Returns true if this Double value is
a Not-a-Number (NaN), false otherwise.
Returns:true if the value represented by this object is
NaN; false otherwise.
isInfinite
public boolean isInfinite()
Returns true if this Double value is
infinitely large in magnitude, false otherwise.
Returns:true if the value represented by this object is
positive infinity
false otherwise.
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.
Overrides: in class
Returns:a String representation of this object.See Also:
public byte byteValue()
Returns the value of this Double as a byte (by
casting to a byte).
Overrides: in class
Returns:the double value represented by this object
converted to type byteSince:
shortValue
public short shortValue()
Returns the value of this Double as a
short (by casting to a short).
Overrides: in class
Returns:the double value represented by this object
converted to type shortSince:
public int intValue()
Returns the value of this Double as an
int (by casting to type int).
Specified by: in class
Returns:the double value represented by this object
converted to type int
public long longValue()
Returns the value of this Double as a
long (by casting to type long).
Specified by: in class
Returns:the double value represented by this object
converted to type long
floatValue
public float floatValue()
Returns the float value of this
Double object.
Specified by: in class
Returns:the double value represented by this object
converted to type floatSince:
doubleValue
public double doubleValue()
Returns the double value of this
Double object.
Specified by: in class
Returns:the double value represented by this object
public 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 , 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());
Overrides: in class
Returns:a hash code value for this object.See Also:,
public boolean equals(&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
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
d1.doubleValue()&== d2.doubleValue()
also has the value true. However, there are two
exceptions:
If d1 and d2 both represent
Double.NaN, then the equals method
returns true, even though
Double.NaN==Double.NaN has the value
If 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.
This definition allows hash tables to operate properly.
Overrides: in class
Parameters:obj - the object to compare with.
Returns:true if the
false otherwise.See Also:
doubleToLongBits
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
0x0000L) represents the sign of the
floating-point number. Bits
62-52 (the bits that are selected by the mask
0x7ff0L) 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
If the argument is negative infinity, the result is
If the argument is NaN, the result is
In all cases, the result is a long integer that, when
given to the
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).
Parameters:value - a double precision floating-point number.
Returns:the bits that represent the floating-point number.
doubleToRawLongBits
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
0x0000L) represents the sign of the
floating-point number. Bits
62-52 (the bits that are selected by the mask
0x7ff0L) 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
If the argument is negative infinity, the result is
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
In all cases, the result is a long integer that,
when given to the
method, will
produce a floating-point value the same as the argument to
doubleToRawLongBits.
Parameters:value - a double precision floating-point number.
Returns:the bits that represent the floating-point number.Since:
longBitsToDouble
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 0x7ff0L, the result
is positive infinity.
If the argument is 0xfff0L, the result
is negative infinity.
If the argument is any value in the range
0x7ff1L through
0x7fffffffffffffffL or in the range
0xfff1L through
0xffffffffffffffffL, the result is a NaN.
754 floating-point operation provided by Java can distinguish
between two NaN values of the same type with different bit
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) | 0x00L;
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.
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
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
although all NaN bit patterns, quiet or signaling,
must be in the NaN range identified above.
Parameters:bits - any long integer.
Returns:the double floating-point value with the same
bit pattern.
public int compareTo(&anotherDouble)
Compares two Double objects numerically.
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.
This ensures that the natural ordering of
Double objects imposed by this method is consistent
with equals.
Specified by: in interface &&
Parameters:anotherDouble - the Double to be compared.
Returns:the value 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.Since:
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))
Parameters:d1 - the first double to compared2 - the second double to compare
Returns:the value 0 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
Java™&PlatformStandard&Ed.&6
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