public final class Double extends Numberimplements Comparable <Double >
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.
| Modifier and Type | Field and Description |
|---|---|
static int |
BYTES
The number of bytes used to represent a
double value.
|
static int |
MAX_EXPONENT
Maximum exponent a finite
double variable may have.
|
static double |
MAX_VALUE
A constant holding the largest positive finite value of type
double, (2-2
-52)·2
1023.
|
static int |
MIN_EXPONENT
Minimum exponent a normalized
double variable may have.
|
static double |
MIN_NORMAL
A constant holding the smallest positive normal value of type
double, 2
-1022.
|
static double |
MIN_VALUE
A constant holding the smallest positive nonzero value of type
double, 2
-1074.
|
static double |
NaN
A constant holding a Not-a-Number (NaN) value of type
double.
|
static double |
NEGATIVE_INFINITY
A constant holding the negative infinity of type
double.
|
static double |
POSITIVE_INFINITY
A constant holding the positive infinity of type
double.
|
static int |
SIZE
The number of bits used to represent a
double value.
|
static Class |
TYPE
The
Class instance representing the primitive type
double.
|
| Constructor and Description |
|---|
Double(double value)
Constructs a newly allocated
Double object that represents the primitive
double argument.
|
Double(String
Constructs a newly allocated
Double object that represents the floating-point value of type
double represented by the string.
|
| Modifier and Type | Method and Description |
|---|---|
byte |
byteValue()
Returns the value of this
Double as a
byte after a narrowing primitive conversion.
|
static int |
compare(double d1, double d2)
Compares the two specified
double values.
|
int |
compareTo(Double
Compares two
Double objects numerically.
|
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.
|
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.
|
double |
doubleValue()
Returns the
double value of this
Double object.
|
boolean |
equals(Object
Compares this object against the specified object.
|
float |
floatValue()
Returns the value of this
Double as a
float after a narrowing primitive conversion.
|
int |
hashCode()
Returns a hash code for this
Double object.
|
static int |
hashCode(double value)
Returns a hash code for a
double value; compatible with
Double.hashCode().
|
int |
intValue()
Returns the value of this
Double as an
int after a narrowing primitive conversion.
|
static boolean |
isFinite(double d)
Returns
true if the argument is a finite floating-point value; returns
false otherwise (for NaN and infinity arguments).
|
boolean |
isInfinite()
Returns
true if this
Double value is infinitely large in magnitude,
false otherwise.
|
static boolean |
isInfinite(double v)
Returns
true if the specified number is infinitely large in magnitude,
false otherwise.
|
boolean |
isNaN()
Returns
true if this
Double value is a Not-a-Number (NaN),
false otherwise.
|
static boolean |
isNaN(double v)
Returns
true if the specified number is a Not-a-Number (NaN) value,
false otherwise.
|
static double |
longBitsToDouble(long bits)
Returns the
double value corresponding to a given bit representation.
|
long |
longValue()
Returns the value of this
Double as a
long after a narrowing primitive conversion.
|
static double |
max(double a, double b)
Returns the greater of two
double values as if by calling
Math.max.
|
static double |
min(double a, double b)
Returns the smaller of two
double values as if by calling
Math.min.
|
static double |
parseDouble(String
Returns a new
double initialized to the value represented by the specified
String, as performed by the
valueOf method of class
Double.
|
short |
shortValue()
Returns the value of this
Double as a
short after a narrowing primitive conversion.
|
static double |
sum(double a, double b)
Adds two
double values together as per the + operator.
|
static String |
toHexString(double d)
Returns a hexadecimal string representation of the
double argument.
|
String |
toString()
Returns a string representation of this
Double object.
|
static String |
toString(double d)
Returns a string representation of the
double argument.
|
static Double |
valueOf(double d)
Returns a
Double instance representing the specified
double value.
|
static Double |
valueOf(String
Returns a
Double object holding the
double value represented by the argument string
s.
|
public static final double POSITIVE_INFINITY
double. It is equal to the value returned by
Double.longBitsToDouble(0x7ff0000000000000L).
public static final double NEGATIVE_INFINITY
double. It is equal to the value returned by
Double.longBitsToDouble(0xfff0000000000000L).
public static final double NaN
double. It is equivalent to the value returned by
Double.longBitsToDouble(0x7ff8000000000000L).
public static final double MAX_VALUE
double, (2-2
-52)·2
1023. 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
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
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
double variable may have. It is equal to the value returned by
Math.getExponent(Double.MAX_VALUE).
public static final int MIN_EXPONENT
double variable may have. It is equal to the value returned by
Math.getExponent(Double.MIN_NORMAL).
public static final int SIZE
double value.
public static final int BYTES
double value.
public Double(double value)
Double object that represents the primitive
double argument.
value - the value to be represented by the
Double.
public Double(Strings) throws NumberFormatException
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 StringtoString(double d)
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 StringtoHexString(double d)
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 DoublevalueOf(String s) throws NumberFormatException
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 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
.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
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 DoublevalueOf(double d)
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(Strings) throws NumberFormatException
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 null
NumberFormatException - if the string does not contain a parsable
double.
valueOf(String)
public static boolean isNaN(double v)
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)
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)
true if the argument is a finite floating-point value; returns
false otherwise (for NaN and infinity arguments).
d - the
double value to be tested
true if the argument is a finite floating-point value,
false otherwise.
public boolean isNaN()
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()
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 StringtoString()
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()
Double as a
byte after a narrowing primitive conversion.
public short shortValue()
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()
Double as an
int after a narrowing primitive conversion.
public long longValue()
Double as a
long after a narrowing primitive conversion.
public float floatValue()
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()
double value of this
Double object.
doubleValue in class
Number
double value represented by this object
public int hashCode()
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)
double value; compatible with
Double.hashCode().
value - the value to hash
double value.
public boolean equals(Objectobj)
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)
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)
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)
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:
Then the floating-point result equals the value of the mathematical expression s· m·2 e-1075.int s = ((bits >> 63) == 0) ? 1 : -1; int e = (int)((bits >> 52) & 0x7ffL); long m = (e == 0) ? (bits & 0xfffffffffffffL) << 1 : (bits & 0xfffffffffffffL) | 0x10000000000000L;
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(DoubleanotherDouble)
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)
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 compare
d2 - the second
double to compare
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
d2.
public static double sum(double a,
double b)
double values together as per the + operator.
a - the first operand
b - the second operand
a and
b
BinaryOperator
public static double max(double a,
double b)
double values as if by calling
Math.max.
a - the first operand
b - the second operand
a and
b
BinaryOperator
public static double min(double a,
double b)
double values as if by calling
Math.min.
a - the first operand
b - the second operand
a and
b.
BinaryOperator