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FlexDoc/Javadoc 2.0 Demo Java Doc |
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.
This is a value-based class; programmers should treat instances that are equal as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail.
An equivalence relation on a set of values is a boolean relation on pairs of values that is reflexive, symmetric, and transitive. For more discussion of equivalence relations and object equality, see the Object.equals specification. An equivalence relation partitions the values it operates over into sets called equivalence classes. All the members of the equivalence class are equal to each other under the relation. An equivalence class may contain only a single member. At least for some purposes, all the members of an equivalence class are substitutable for each other. In particular, in a numeric expression equivalent values can be substituted for one another without changing the result of the expression, meaning changing the equivalence class of the result of the expression.
Notably, the built-in == operation on floating-point values is not an equivalence relation. Despite not defining an equivalence relation, the semantics of the IEEE 754 == operator were deliberately designed to meet other needs of numerical computation. There are two exceptions where the properties of an equivalence relation are not satisfied by == on floating-point values:
For ordered comparisons using the built-in comparison operators (<, <=, etc.), NaN values have another anomalous situation: a NaN is neither less than, nor greater than, nor equal to any value, including itself. This means the trichotomy of comparison does not hold.
To provide the appropriate semantics for equals and compareTo methods, those methods cannot simply be wrappers around == or ordered comparison operations. Instead, equals defines NaN arguments to be equal to each other and defines +0.0 to not be equal to -0.0, restoring reflexivity. For comparisons, compareTo defines a total order where -0.0 is less than +0.0 and where a NaN is equal to itself and considered greater than positive infinity.
The operational semantics of equals and compareTo are expressed in terms of bit-wise converting the floating-point values to integral values.
The natural ordering implemented by compareTo is consistent with equals. That is, two objects are reported as equal by equals if and only if compareTo on those objects returns zero.
The adjusted behaviors defined for equals and compareTo allow instances of wrapper classes to work properly with conventional data structures. For example, defining NaN values to be equals to one another allows NaN to be used as an element of a HashSet or as the key of a HashMap. Similarly, defining compareTo as a total ordering, including +0.0, -0.0, and NaN, allows instances of wrapper classes to be used as elements of a SortedSet or as keys of a SortedMap.
Field Summary |
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static final int |
The number of bytes used to represent a double value.
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static final int |
Maximum exponent a finite double variable may have.
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static final double |
A constant holding the largest positive finite value of type
double,
(2-2-52)·21023.
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static final int |
Minimum exponent a normalized double variable may
have.
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static final double |
A constant holding the smallest positive normal value of type
double, 2-1022.
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static final double |
A constant holding the smallest positive nonzero value of type
double, 2-1074.
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static final double |
A constant holding a Not-a-Number (NaN) value of type
double.
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static final double |
A constant holding the negative infinity of type
double.
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static final double |
A constant holding the positive infinity of type
double.
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static final int |
The number of bits used to represent a double value.
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The Class instance representing the primitive type
double.
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Constructor Summary |
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Double(double value)
Deprecated, for removal. It is rarely appropriate to use this constructor.
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Deprecated, for removal. It is rarely appropriate to use this constructor.
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Method Summary |
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byte |
Returns the value of this Double as a byte
after a narrowing primitive conversion.
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static int |
compare(double d1, double d2)
Compares the two specified double values.
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int |
Compares two Double objects numerically.
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Returns an Optional containing the nominal descriptor for this
instance, which is the instance itself.
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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.
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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.
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double |
Returns the double value of this Double object.
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boolean |
Compares this object against the specified object.
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float |
Returns the value of this Double as a float
after a narrowing primitive conversion.
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int |
hashCode()
Returns a hash code for this Double object.
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static int |
hashCode(double value)
Returns a hash code for a double value; compatible with
Double.hashCode().
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int |
intValue()
Returns the value of this Double as an int
after a narrowing primitive conversion.
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static boolean |
isFinite(double d)
Returns true if the argument is a finite floating-point
value; returns false otherwise (for NaN and infinity
arguments).
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boolean |
Returns true if this Double value is
infinitely large in magnitude, false otherwise.
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static boolean |
isInfinite(double v)
Returns true if the specified number is infinitely
large in magnitude, false otherwise.
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boolean |
isNaN()
Returns true if this Double value is
a Not-a-Number (NaN), false otherwise.
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static boolean |
isNaN(double v)
Returns true if the specified number is a
Not-a-Number (NaN) value, false otherwise.
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static double |
longBitsToDouble(long bits)
Returns the double value corresponding to a given
bit representation.
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long |
Returns the value of this Double as a long
after a narrowing primitive conversion.
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static double |
max(double a, double b)
Returns the greater of two double values
as if by calling Math.max.
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static double |
min(double a, double b)
Returns the smaller of two double values
as if by calling Math.min.
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static double |
Returns a new double initialized to the value
represented by the specified String, as performed
by the valueOf method of class
Double.
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Resolves this instance as a ConstantDesc, the result of which is
the instance itself.
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short |
Returns the value of this Double as a short
after a narrowing primitive conversion.
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static double |
sum(double a, double b)
Adds two double values together as per the + operator.
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static String |
toHexString(double d)
Returns a hexadecimal string representation of the
double argument.
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toString()
Returns a string representation of this Double object.
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static String |
toString(double d)
Returns a string representation of the double
argument.
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static Double |
valueOf(double d)
Returns a Double instance representing the specified
double value.
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static Double |
Returns a Double object holding the
double value represented by the argument string
s.
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Methods inherited from class java.lang.Object |
public Double |
(double value) |
public Double |
(String s) |
throws |
public static String toString |
(double d) |
To create localized string representations of a floating-point value, use subclasses of NumberFormat.
public static String toHexString |
(double d) |
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 |
public static Double valueOf |
(String s) |
throws |
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 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.
- 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
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
}
public static Double valueOf |
(double d) |
public static double parseDouble |
(String s) |
throws |
public static boolean isNaN |
(double v) |
public static boolean isInfinite |
(double v) |
public static boolean isFinite |
(double d) |
public boolean isNaN |
() |
public boolean isInfinite |
() |
public String toString |
() |
public byte byteValue |
() |
public short shortValue |
() |
public int intValue |
() |
public long longValue |
() |
public float floatValue |
() |
public double doubleValue |
() |
public int hashCode |
() |
(int)(v^(v>>>32))where v is defined by:
long v = Double.doubleToLongBits(this.doubleValue());
public static int hashCode |
(double value) |
public boolean equals |
(Object obj) |
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).
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.
public static double longBitsToDouble |
(long bits) |
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.
public int compareTo |
(Double anotherDouble) |
public static int compare |
(double d1, double d2) |
new Double(d1).compareTo(new Double(d2))
public static double sum |
(double a, double b) |
public static double max |
(double a, double b) |
public static double min |
(double a, double b) |
() |
public Double resolveConstantDesc |
(MethodHandles.Lookup lookup) |
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