Class Double

java.lang.Object
java.lang.Number
java.lang.Double
All Implemented Interfaces:
Serializable,Comparable<Double>,Constable,ConstantDesc
public final classDoubleextendsNumberimplementsComparable<Double>,Constable,ConstantDesc
TheDouble class is thewrapper class for values of the primitive typedouble. An object of typeDouble contains a single field whose type isdouble.

In addition, this class provides several methods for converting adouble to aString and aString to adouble, as well as other constants and methods useful when dealing with adouble.

This is avalue-based class; programmers should treat instances that areequal as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail.

Floating-point Equality, Equivalence, and Comparison

IEEE 754 floating-point values include finite nonzero values, signed zeros (+0.0 and-0.0), signed infinities (positive infinity andnegative infinity), andNaN (not-a-number).

Anequivalence 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 theObject.equals specification. An equivalence relation partitions the values it operates over into sets calledequivalence 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 besubstituted 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 isnot 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:

  • Ifv1 andv2 are both NaN, thenv1 == v2 has the valuefalse. Therefore, for two NaN arguments thereflexive property of an equivalence relation isnot satisfied by the== operator.
  • Ifv1 represents+0.0 whilev2 represents-0.0, or vice versa, thenv1 == v2 has the valuetrue even though+0.0 and-0.0 are distinguishable under various floating-point operations. For example,1.0/+0.0 evaluates to positive infinity while1.0/-0.0 evaluates tonegative infinity and positive infinity and negative infinity are neither equal to each other nor equivalent to each other. Thus, while a signed zero input most commonly determines the sign of a zero result, because of dividing by zero,+0.0 and-0.0 may not be substituted for each other in general. The sign of a zero input also has a non-substitutable effect on the result of some math library methods.

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 thetrichotomy of comparison doesnot hold.

To provide the appropriate semantics forequals andcompareTo methods, those methods cannot simply be wrappers around== or ordered comparison operations. Instead,equals usesrepresentation equivalence, defining NaN arguments to be equal to each other, restoring reflexivity, and defining+0.0 tonot be equal to-0.0. 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 ofequals and compareTo are expressed in terms ofbit-wise converting the floating-point values to integral values.

Thenatural ordering implemented bycompareTo isconsistent with equals. That is, two objects are reported as equal byequals if and only ifcompareTo on those objects returns zero.

The adjusted behaviors defined forequals and compareTo allow instances of wrapper classes to work properly with conventional data structures. For example, defining NaN values to beequals to one another allows NaN to be used as an element of aHashSet or as the key of aHashMap. 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 aSortedSet or as keys of aSortedMap.

Comparing numerical equality to various useful equivalence relations that can be defined over floating-point values:

numerical equality (== operator): (Not an equivalence relation)
Two floating-point values represent the same extended real number. The extended real numbers are the real numbers augmented with positive infinity and negative infinity. Under numerical equality,+0.0 and-0.0 are equal since they both map to the same real value, 0. A NaN does not map to any real number and is not equal to any value, including itself.
bit-wise equivalence:
The bits of the two floating-point values are the same. This equivalence relation fordouble valuesa and b is implemented by the expression
Double.doubleToRawLongBits(a) == Double.doubleToRawLongBits(b)
Under this relation,+0.0 and-0.0 are distinguished from each other and every bit pattern encoding a NaN is distinguished from every other bit pattern encoding a NaN.
representation equivalence:
The two floating-point values represent the same IEEE 754datum. In particular, forfinite values, the sign,exponent, and significand components of the floating-point values are the same. Under this relation:
  • +0.0 and-0.0 are distinguished from each other.
  • every bit pattern encoding a NaN is considered equivalent to each other
  • positive infinity is equivalent to positive infinity; negative infinity is equivalent to negative infinity.
Expressions implementing this equivalence relation include:
  • Double.doubleToLongBits(a) == Double.doubleToLongBits(b)
  • Double.valueOf(a).equals(Double.valueOf(b))
  • Double.compare(a, b) == 0
Note that representation equivalence is often an appropriate notion of equivalence to test the behavior ofmath libraries.
For two binary floating-point valuesa andb, if neither ofa andb is zero or NaN, then the three relations numerical equality, bit-wise equivalence, and representation equivalence ofa andb have the sametrue/false value. In other words, for binary floating-point values, the three relations only differ if at least one argument is zero or NaN.

Decimal ↔ Binary Conversion Issues

Many surprising results of binary floating-point arithmetic trace back to aspects of decimal to binary conversion and binary to decimal conversion. While integer values can be exactly represented in any base, which fractional values can be exactly represented in a base is a function of the base. For example, in base 10, 1/3 is a repeating fraction (0.33333....); but in base 3, 1/3 is exactly 0.1(3), that is 1 × 3-1. Similarly, in base 10, 1/10 is exactly representable as 0.1 (1 × 10-1), but in base 2, it is a repeating fraction (0.0001100110011...(2)).

Values of thefloat type have24 bits of precision and values of thedouble type have53 bits of precision. Therefore, since 0.1 is a repeating fraction in base 2 with a four-bit repeat, 0.1f !=0.1d. In more detail, including hexadecimal floating-point literals:

  • The exact numerical value of0.1f (0x1.99999a0000000p-4f) is 0.100000001490116119384765625.
  • The exact numerical value of0.1d (0x1.999999999999ap-4d) is 0.1000000000000000055511151231257827021181583404541015625.
These are the closestfloat anddouble values, respectively, to the numerical value of 0.1. These results are consistent with afloat value having the equivalent of 6 to 9 digits of decimal precision and adouble value having the equivalent of 15 to 17 digits of decimal precision. (The equivalent precision varies according to the different relative densities of binary and decimal values at different points along the real number line.)

This representation hazard of decimal fractions is one reason to use caution when storing monetary values asfloat or double. Alternatives include:

  • usingBigDecimal to store decimal fractional values exactly
  • scaling up so the monetary value is an integer — for example, multiplying by 100 if the value is denominated in cents or multiplying by 1000 if the value is denominated in mills — and then storing that scaled value in an integer type

For each finite floating-point value and a given floating-point type, there is a contiguous region of the real number line which maps to that value. Under the default round to nearest rounding policy (JLS15.4), this contiguous region for a value is typically oneulp (unit in the last place) wide and centered around the exactly representable value. (At exponent boundaries, the region is asymmetrical and larger on the side with the larger exponent.) For example, for0.1f, the region can be computed as follows:
// Numeric values listed are exact values
oneTenthApproxAsFloat = 0.100000001490116119384765625;
ulpOfoneTenthApproxAsFloat = Math.ulp(0.1f) = 7.450580596923828125E-9;
// Numeric range that is converted to the float closest to 0.1, _excludes_ endpoints
(oneTenthApproxAsFloat - ½ulpOfoneTenthApproxAsFloat, oneTenthApproxAsFloat + ½ulpOfoneTenthApproxAsFloat) =
(0.0999999977648258209228515625, 0.1000000052154064178466796875)

In particular, a correctly rounded decimal to binary conversion of any string representing a number in this range, say byFloat.parseFloat(String), will be converted to the same value:

Float.parseFloat("0.0999999977648258209228515625000001"); // rounds up to oneTenthApproxAsFloatFloat.parseFloat("0.099999998");                          // rounds up to oneTenthApproxAsFloatFloat.parseFloat("0.1");                                  // rounds up to oneTenthApproxAsFloatFloat.parseFloat("0.100000001490116119384765625");        // exact conversionFloat.parseFloat("0.100000005215406417846679687");        // rounds down to oneTenthApproxAsFloatFloat.parseFloat("0.100000005215406417846679687499999");  // rounds down to oneTenthApproxAsFloat

Similarly, an analogous range can be constructed for the double type based on the exact value ofdouble approximation to0.1d and the numerical value of Math.ulp(0.1d) and likewise for other particular numerical values in thefloat anddouble types.

As seen in the above conversions, compared to the exact numerical value the operation would have without rounding, the same floating-point value as a result can be:

  • greater than the exact result
  • equal to the exact result
  • less than the exact result
A floating-point value doesn't "know" whether it was the result of rounding up, or rounding down, or an exact operation; it contains no history of how it was computed. Consequently, the sum of
0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f;// Numerical value of computed sum: 1.00000011920928955078125,// the next floating-point value larger than 1.0f, equal to Math.nextUp(1.0f).
or
0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d;// Numerical value of computed sum: 0.99999999999999988897769753748434595763683319091796875,// the next floating-point value smaller than 1.0d, equal to Math.nextDown(1.0d).
shouldnot be expected to be exactly equal to 1.0, but only to be close to 1.0. Consequently, the following code is an infinite loop:
double d = 0.0;while (d != 1.0) { // Surprising infinite loop  d += 0.1; // Sum never _exactly_ equals 1.0}
Instead, use an integer loop count for counted loops:
double d = 0.0;for (int i = 0; i < 10; i++) {  d += 0.1;} // Value of d is equal to Math.nextDown(1.0).
or test against a floating-point limit using ordered comparisons (<,<=,>,>=):
double d = 0.0;while (d <= 1.0) {  d += 0.1;} // Value of d approximately 1.0999999999999999
While floating-point arithmetic may have surprising results, IEEE 754 floating-point arithmetic follows a principled design and its behavior is predictable on the Java platform.

SeeJava Language Specification:
4.2.3 Floating-Point Types and Values
4.2.4 Floating-Point Operations
15.21.1 Numerical Equality Operators == and !=
15.20.1 Numerical Comparison Operators<,<=,>, and>=
Since:
1.0
External Specifications
See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    The number of bytes used to represent adouble value, 8.
    static final int
    Maximum exponent a finitedouble variable may have, 1023.
    static final double
    A constant holding the largest positive finite value of typedouble, (2-2-52)·21023.
    static final int
    Minimum exponent a normalizeddouble variable may have, -1022.
    static final double
    A constant holding the smallest positive normal value of typedouble, 2-1022.
    static final double
    A constant holding the smallest positive nonzero value of typedouble, 2-1074.
    static final double
    A constant holding a Not-a-Number (NaN) value of typedouble.
    static final double
    A constant holding the negative infinity of typedouble.
    static final double
    A constant holding the positive infinity of typedouble.
    static final int
    The number of bits in the significand of adouble value, 53.
    static final int
    The number of bits used to represent adouble value, 64.
    static finalClass<Double>
    TheClass instance representing the primitive typedouble.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Double(double value)
    Deprecated, for removal: This API element is subject to removal in a future version.
    It is rarely appropriate to use this constructor.
    Deprecated, for removal: This API element is subject to removal in a future version.
    It is rarely appropriate to use this constructor.

  • Method Summary

    Modifier and Type
    Method
    Description
    byte
    Returns the value of thisDouble as abyte after a narrowing primitive conversion.
    static int
    compare(double d1, double d2)
    Compares the two specifieddouble values.
    int
    compareTo(Double anotherDouble)
    Compares twoDouble objects numerically.
    Returns anOptional containing the nominal descriptor for this instance, which is the instance itself.
    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
    Returns thedouble value of thisDouble object.
    boolean
    Compares this object against the specified object.
    float
    Returns the value of thisDouble as afloat after a narrowing primitive conversion.
    int
    Returns a hash code for thisDouble object.
    static int
    hashCode(double value)
    Returns a hash code for adouble value; compatible withDouble.hashCode().
    int
    Returns the value of thisDouble as anint after a narrowing primitive conversion.
    static boolean
    isFinite(double d)
    Returnstrue if the argument is a finite floating-point value; returnsfalse otherwise (for NaN and infinity arguments).
    boolean
    Returnstrue if thisDouble value is infinitely large in magnitude,false otherwise.
    static boolean
    isInfinite(double v)
    Returnstrue if the specified number is infinitely large in magnitude,false otherwise.
    boolean
    Returnstrue if thisDouble value is a Not-a-Number (NaN),false otherwise.
    static boolean
    isNaN(double v)
    Returnstrue if the specified number is a Not-a-Number (NaN) value,false otherwise.
    static double
    longBitsToDouble(long bits)
    Returns thedouble value corresponding to a given bit representation.
    long
    Returns the value of thisDouble as along after a narrowing primitive conversion.
    static double
    max(double a, double b)
    Returns the greater of twodouble values as if by callingMath.max.
    static double
    min(double a, double b)
    Returns the smaller of twodouble values as if by callingMath.min.
    static double
    Returns a newdouble initialized to the value represented by the specifiedString, as performed by thevalueOf method of classDouble.
    Resolves this instance as aConstantDesc, the result of which is the instance itself.
    short
    Returns the value of thisDouble as ashort after a narrowing primitive conversion.
    static double
    sum(double a, double b)
    Adds twodouble values together as per the + operator.
    staticString
    toHexString(double d)
    Returns a hexadecimal string representation of thedouble argument.
    Returns a string representation of thisDouble object.
    staticString
    toString(double d)
    Returns a string representation of thedouble argument.
    staticDouble
    valueOf(double d)
    Returns aDouble instance representing the specifieddouble value.
    staticDouble
    Returns aDouble object holding thedouble value represented by the argument strings.

    Methods declared in class java.lang.Object

    clone,finalize,getClass,notify,notifyAll,wait,wait,wait

  • Field Details

    • POSITIVE_INFINITY

      public static final double POSITIVE_INFINITY
      A constant holding the positive infinity of typedouble. It is equal to the value returned byDouble.longBitsToDouble(0x7ff0000000000000L).
      See Also:

    • NEGATIVE_INFINITY

      public static final double NEGATIVE_INFINITY
      A constant holding the negative infinity of typedouble. It is equal to the value returned byDouble.longBitsToDouble(0xfff0000000000000L).
      See Also:

    • NaN

      public static final double NaN
      A constant holding a Not-a-Number (NaN) value of typedouble. It isequivalent to the value returned byDouble.longBitsToDouble(0x7ff8000000000000L).
      See Also:

    • MAX_VALUE

      public static final double MAX_VALUE
      A constant holding the largest positive finite value of typedouble, (2-2-52)·21023. It is equal to the hexadecimal floating-point literal0x1.fffffffffffffP+1023 and also equal toDouble.longBitsToDouble(0x7fefffffffffffffL).
      See Also:

    • MIN_NORMAL

      public static final double MIN_NORMAL
      A constant holding the smallest positive normal value of typedouble, 2-1022. It is equal to the hexadecimal floating-point literal0x1.0p-1022 and also equal toDouble.longBitsToDouble(0x0010000000000000L).
      Since:
      1.6
      See Also:

    • MIN_VALUE

      public static final double MIN_VALUE
      A constant holding the smallest positive nonzero value of typedouble, 2-1074. It is equal to the hexadecimal floating-point literal0x0.0000000000001P-1022 and also equal toDouble.longBitsToDouble(0x1L).
      See Also:

    • SIZE

      public static final int SIZE
      The number of bits used to represent adouble value, 64.
      Since:
      1.5
      See Also:

    • PRECISION

      public static final int PRECISION
      The number of bits in the significand of adouble value, 53. This is the parameter N in section4.2.3 ofThe Java Language Specification.
      Since:
      19
      See Also:

    • MAX_EXPONENT

      public static final int MAX_EXPONENT
      Maximum exponent a finitedouble variable may have, 1023. It is equal to the value returned by Math.getExponent(Double.MAX_VALUE).
      Since:
      1.6
      See Also:

    • MIN_EXPONENT

      public static final int MIN_EXPONENT
      Minimum exponent a normalizeddouble variable may have, -1022. It is equal to the value returned by Math.getExponent(Double.MIN_NORMAL).
      Since:
      1.6
      See Also:

    • BYTES

      public static final int BYTES
      The number of bytes used to represent adouble value, 8.
      Since:
      1.8
      See Also:

    • TYPE

      public static final Class<Double> TYPE
      TheClass instance representing the primitive typedouble.
      Since:
      1.1

  • Constructor Details

    • Double

      @Deprecated(since="9",forRemoval=true)public Double(double value)
      Deprecated, for removal: This API element is subject to removal in a future version.
      It is rarely appropriate to use this constructor. The static factoryvalueOf(double) is generally a better choice, as it is likely to yield significantly better space and time performance.
      Constructs a newly allocatedDouble object that represents the primitivedouble argument.
      Parameters:
      value - the value to be represented by theDouble.

    • Double

      @Deprecated(since="9",forRemoval=true)public Double(String s) throwsNumberFormatException
      Deprecated, for removal: This API element is subject to removal in a future version.
      It is rarely appropriate to use this constructor. UseparseDouble(String) to convert a string to adouble primitive, or usevalueOf(String) to convert a string to aDouble object.
      Constructs a newly allocatedDouble object that represents the floating-point value of typedouble represented by the string. The string is converted to adouble value as if by thevalueOf method.
      Parameters:
      s - a string to be converted to aDouble.
      Throws:
      NumberFormatException - if the string does not contain a parsable number.

  • Method Details

    • toString

      public static String toString(double d)
      Returns a string representation of thedouble argument. All characters mentioned below are ASCII characters.
      • If the argument is NaN, the result is the string "NaN".
      • 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 magnitudem:
        • Ifm is infinity, it is represented by the characters"Infinity"; thus, positive infinity produces the result"Infinity" and negative infinity produces the result"-Infinity".
        • Ifm is zero, it is represented by the characters"0.0"; thus, negative zero produces the result"-0.0" and positive zero produces the result"0.0".
        • Otherwisem is positive and finite. It is converted to a string in two stages:
          • Selection of a decimal: A well-defined decimaldm is selected to representm. This decimal is (almost always) theshortest one that rounds tom according to the round to nearest rounding policy of IEEE 754 floating-point arithmetic.
          • Formatting as a string: The decimaldm is formatted as a string, either in plain or in computerized scientific notation, depending on its value.

      Adecimal is a number of the forms×10i for some (unique) integerss > 0 andi such thats is not a multiple of 10. These integers are thesignificand and theexponent, respectively, of the decimal. Thelength of the decimal is the (unique) positive integern meeting 10n-1 ≤s < 10n.

      The decimaldm for a finite positivem is defined as follows:

      • LetR be the set of all decimals that round tom according to the usualround to nearest rounding policy of IEEE 754 floating-point arithmetic.
      • Letp be the minimal length over all decimals inR.
      • Whenp ≥ 2, letT be the set of all decimals inR with lengthp. Otherwise, letT be the set of all decimals inR with length 1 or 2.
      • Definedm as the decimal inT that is closest tom. Or if there are two such decimals inT, select the one with the even significand.

      The (uniquely) selected decimaldm is then formatted. Lets,i andn be the significand, exponent and length ofdm, respectively. Further, lete =n +i - 1 and lets1…sn be the usual decimal expansion ofs. Note thats1 ≠ 0 andsn ≠ 0. Below, the decimal point'.' is'\u002E' and the exponent indicator'E' is'\u0045'.

      • Case -3 ≤e < 0:dm is formatted as0.0…0s1…sn, where there are exactly -(n +i) zeroes between the decimal point ands1. For example, 123 × 10-4 is formatted as0.0123.
      • Case 0 ≤e < 7:
        • Subcasei ≥ 0:dm is formatted ass1…sn0…0.0, where there are exactlyi zeroes betweensn and the decimal point. For example, 123 × 102 is formatted as12300.0.
        • Subcasei < 0:dm is formatted ass1…sn+i.sn+i+1…sn, where there are exactly -i digits to the right of the decimal point. For example, 123 × 10-1 is formatted as12.3.
      • Casee < -3 ore ≥ 7: computerized scientific notation is used to formatdm. Heree is formatted as byInteger.toString(int).
        • Subcasen = 1:dm is formatted ass1.0Ee. For example, 1 × 1023 is formatted as1.0E23.
        • Subcasen > 1:dm is formatted ass1.s2…snEe. For example, 123 × 10-21 is formatted as1.23E-19.

      To create localized string representations of a floating-point value, use subclasses ofNumberFormat.

      API Note:
      This method corresponds to the general functionality of the convertToDecimalCharacter operation defined in IEEE 754; however, that operation is defined in terms of specifying the number of significand digits used in the conversion. Code to do such a conversion in the Java platform includes converting thedouble to aBigDecimal exactly and then rounding theBigDecimal to the desired number of digits; sample code:
      double d = 0.1;int digits = 25;BigDecimal bd = new BigDecimal(d);String result = bd.round(new MathContext(digits,  RoundingMode.HALF_UP));// 0.1000000000000000055511151
      Parameters:
      d - thedouble to be converted.
      Returns:
      a string representation of the argument.

    • toHexString

      public static String toHexString(double d)
      Returns a hexadecimal string representation of thedouble argument. All characters mentioned below are ASCII characters.
      • If the argument is NaN, the result is the string "NaN".
      • 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 magnitudem:
        • Ifm is infinity, it is represented by the string"Infinity"; thus, positive infinity produces the result"Infinity" and negative infinity produces the result"-Infinity".
        • Ifm 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".
        • Ifm is adouble 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 toInteger.toString on the exponent value.
        • Ifm is adouble 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.
      Examples
      Floating-point ValueHexadecimal String
      1.00x1.0p0
      -1.0-0x1.0p0
      2.00x1.0p1
      3.00x1.8p1
      0.50x1.0p-1
      0.250x1.0p-2
      Double.MAX_VALUE0x1.fffffffffffffp1023
      Minimum Normal Value0x1.0p-1022
      Maximum Subnormal Value0x0.fffffffffffffp-1022
      Double.MIN_VALUE0x0.0000000000001p-1022
      API Note:
      This method corresponds to the convertToHexCharacter operation defined in IEEE 754.
      Parameters:
      d - thedouble to be converted.
      Returns:
      a hex string representation of the argument.
      Since:
      1.5

    • valueOf

      public static Double valueOf(String s) throwsNumberFormatException
      Returns aDouble object holding thedouble value represented by the argument strings.

      Ifs isnull, then aNullPointerException is thrown.

      Leading and trailing whitespace characters ins are ignored. Whitespace is removed as if by theString.trim() method; that is, both ASCII space and control characters are removed. The rest ofs should constitute aFloatValue as described by the lexical syntax rules:

      FloatValue:
      SignoptNaN
      SignoptInfinity
      Signopt FloatingPointLiteral
      Signopt HexFloatingPointLiteral
      SignedInteger
      HexFloatingPointLiteral:
      HexSignificand BinaryExponent FloatTypeSuffixopt
      HexSignificand:
      HexNumeral
      HexNumeral.
      0xHexDigitsopt. HexDigits
      0X HexDigitsopt.HexDigits
      BinaryExponent:
      BinaryExponentIndicator SignedInteger
      BinaryExponentIndicator:
      p
      P
      whereSign,FloatingPointLiteral,HexNumeral,HexDigits,SignedInteger andFloatTypeSuffix are as defined in the lexical structure sections ofThe Java Language Specification, except that underscores are not accepted between digits. Ifs does not have the form of aFloatValue, then aNumberFormatException 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 typedouble 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 ofs is large enough in magnitude (greater than or equal to (MAX_VALUE +ulp(MAX_VALUE)/2), rounding todouble will result in an infinity and if the exact value ofs is small enough in magnitude (less than or equal toMIN_VALUE/2), rounding to float will result in a zero. Finally, after rounding aDouble object representing thisdouble value is returned.

      Note that trailing format specifiers, specifiers that determine the type of a floating-point literal (1.0f is afloat value;1.0d is adouble value), donot 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 tofloat followed byfloat todouble, isnot equivalent to converting a string directly todouble. For example, thefloat literal0.1f is equal to thedouble value0.10000000149011612; thefloat literal0.1f represents a different numerical value than thedouble literal0.1. (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 aNumberFormatException 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 }

      API Note:
      To interpret localized string representations of a floating-point value, or string representations that have non-ASCII digits, useNumberFormat. For example,
          NumberFormat.getInstance(l).parse(s).doubleValue();
      wherel is the desired locale, orLocale.ROOT if locale insensitive., This method corresponds to the convertFromDecimalCharacter and convertFromHexCharacter operations defined in IEEE 754.
      Parameters:
      s - the string to be parsed.
      Returns:
      aDouble object holding the value represented by theString argument.
      Throws:
      NumberFormatException - if the string does not contain a parsable number.
      See Also:

    • valueOf

      public static Double valueOf(double d)
      Returns aDouble instance representing the specifieddouble value. If a newDouble instance is not required, this method should generally be used in preference to the constructorDouble(double), as this method is likely to yield significantly better space and time performance by caching frequently requested values.
      Parameters:
      d - a double value.
      Returns:
      aDouble instance representingd.
      Since:
      1.5

    • parseDouble

      public static double parseDouble(String s) throwsNumberFormatException
      Returns a newdouble initialized to the value represented by the specifiedString, as performed by thevalueOf method of classDouble.
      Parameters:
      s - the string to be parsed.
      Returns:
      thedouble value represented by the string argument.
      Throws:
      NullPointerException - if the string is null
      NumberFormatException - if the string does not contain a parsabledouble.
      Since:
      1.2
      See Also:

    • isNaN

      public static boolean isNaN(double v)
      Returnstrue if the specified number is a Not-a-Number (NaN) value,false otherwise.
      API Note:
      This method corresponds to the isNaN operation defined in IEEE 754.
      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)
      Returnstrue if the specified number is infinitely large in magnitude,false otherwise.
      API Note:
      This method corresponds to the isInfinite operation defined in IEEE 754.
      Parameters:
      v - the value to be tested.
      Returns:
      true if the value of the argument is positive infinity or negative infinity;false otherwise.

    • isFinite

      public static boolean isFinite(double d)
      Returnstrue if the argument is a finite floating-point value; returnsfalse otherwise (for NaN and infinity arguments).
      API Note:
      This method corresponds to the isFinite operation defined in IEEE 754.
      Parameters:
      d - thedouble value to be tested
      Returns:
      true if the argument is a finite floating-point value,false otherwise.
      Since:
      1.8

    • isNaN

      public boolean isNaN()
      Returnstrue if thisDouble 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()
      Returnstrue if thisDouble value is infinitely large in magnitude,false otherwise.
      Returns:
      true if the value represented by this object is positive infinity or negative infinity;false otherwise.

    • toString

      public String toString()
      Returns a string representation of thisDouble object. The primitivedouble value represented by this object is converted to a string exactly as if by the methodtoString of one argument.
      Overrides:
      toString in class Object
      Returns:
      aString representation of this object.
      See Also:

    • byteValue

      public byte byteValue()
      Returns the value of thisDouble as abyte after a narrowing primitive conversion.
      Overrides:
      byteValue in class Number
      Returns:
      thedouble value represented by this object converted to typebyte
      SeeJava Language Specification:
      5.1.3 Narrowing Primitive Conversion
      Since:
      1.1

    • shortValue

      public short shortValue()
      Returns the value of thisDouble as ashort after a narrowing primitive conversion.
      Overrides:
      shortValue in class Number
      Returns:
      thedouble value represented by this object converted to typeshort
      SeeJava Language Specification:
      5.1.3 Narrowing Primitive Conversion
      Since:
      1.1

    • intValue

      public int intValue()
      Returns the value of thisDouble as anint after a narrowing primitive conversion.
      Specified by:
      intValue in class Number
      API Note:
      This method corresponds to the convertToIntegerTowardZero operation defined in IEEE 754.
      Returns:
      thedouble value represented by this object converted to typeint
      SeeJava Language Specification:
      5.1.3 Narrowing Primitive Conversion

    • longValue

      public long longValue()
      Returns the value of thisDouble as along after a narrowing primitive conversion.
      Specified by:
      longValue in class Number
      API Note:
      This method corresponds to the convertToIntegerTowardZero operation defined in IEEE 754.
      Returns:
      thedouble value represented by this object converted to typelong
      SeeJava Language Specification:
      5.1.3 Narrowing Primitive Conversion

    • floatValue

      public float floatValue()
      Returns the value of thisDouble as afloat after a narrowing primitive conversion.
      Specified by:
      floatValue in class Number
      API Note:
      This method corresponds to the convertFormat operation defined in IEEE 754.
      Returns:
      thedouble value represented by this object converted to typefloat
      SeeJava Language Specification:
      5.1.3 Narrowing Primitive Conversion
      Since:
      1.0

    • doubleValue

      public double doubleValue()
      Returns thedouble value of thisDouble object.
      Specified by:
      doubleValue in class Number
      Returns:
      thedouble value represented by this object

    • hashCode

      public int hashCode()
      Returns a hash code for thisDouble object. The result is the exclusive OR of the two halves of thelong integer bit representation, exactly as produced by the methoddoubleToLongBits(double), of the primitivedouble value represented by thisDouble object. That is, the hash code is the value of the expression:
      (int)(v^(v>>>32))
      wherev is defined by:
      long v = Double.doubleToLongBits(this.doubleValue());
      Overrides:
      hashCode in class Object
      Returns:
      ahash code value for this object.
      See Also:

    • hashCode

      public static int hashCode(double value)
      Returns a hash code for adouble value; compatible withDouble.hashCode().
      Parameters:
      value - the value to hash
      Returns:
      a hash code value for adouble value.
      Since:
      1.8

    • equals

      public boolean equals(Object obj)
      Compares this object against the specified object. The result istrue if and only if the argument is notnull and is aDouble object that represents adouble that has the same value as thedouble represented by this object. For this purpose, twodouble values are considered to be the same if and only if the methoddoubleToLongBits(double) returns the identicallong value when applied to each.
      Overrides:
      equals in class Object
      API Note:
      This method is defined in terms ofdoubleToLongBits(double) rather than the== operator ondouble values since the== operator doesnot define an equivalence relation and to satisfy theequals contract an equivalence relation must be implemented; seethis discussion for details of floating-point equality and equivalence.
      Parameters:
      obj - the reference object with which to compare.
      Returns:
      true if this object is the same as the obj argument;false otherwise.
      SeeJava Language Specification:
      15.21.1 Numerical Equality Operators == and !=
      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 mask0x8000000000000000L) represents the sign of the floating-point number. Bits 62-52 (the bits that are selected by the mask0x7ff0000000000000L) represent the exponent. Bits 51-0 (the bits that are selected by the mask0x000fffffffffffffL) represent the significand (sometimes called the mantissa) of the floating-point number.

      If the argument is positive infinity, the result is0x7ff0000000000000L.

      If the argument is negative infinity, the result is0xfff0000000000000L.

      If the argument is NaN, the result is0x7ff8000000000000L.

      In all cases, the result is along integer that, when given to thelongBitsToDouble(long) method, will produce a floating-point value the same as the argument todoubleToLongBits (except all NaN values are collapsed to a single "canonical" NaN value).

      Parameters:
      value - adouble 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 mask0x8000000000000000L) represents the sign of the floating-point number. Bits 62-52 (the bits that are selected by the mask0x7ff0000000000000L) represent the exponent. Bits 51-0 (the bits that are selected by the mask0x000fffffffffffffL) represent the significand (sometimes called the mantissa) of the floating-point number.

      If the argument is positive infinity, the result is0x7ff0000000000000L.

      If the argument is negative infinity, the result is0xfff0000000000000L.

      If the argument is NaN, the result is thelong integer representing the actual NaN value. Unlike thedoubleToLongBits method,doubleToRawLongBits does not collapse all the bit patterns encoding a NaN to a single "canonical" NaN value.

      In all cases, the result is along integer that, when given to thelongBitsToDouble(long) method, will produce a floating-point value the same as the argument todoubleToRawLongBits.

      Parameters:
      value - adouble precision floating-point number.
      Returns:
      the bits that represent the floating-point number.
      Since:
      1.3

    • longBitsToDouble

      public static double longBitsToDouble(long bits)
      Returns thedouble 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 is0x7ff0000000000000L, the result is positive infinity.

      If the argument is0xfff0000000000000L, the result is negative infinity.

      If the argument is any value in the range0x7ff0000000000001L through0x7fffffffffffffffL or in the range0xfff0000000000001L through0xffffffffffffffffL, 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 theDouble.doubleToRawLongBits method.

      In all other cases, lets,e, andm 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 expressions·m·2e-1075.

      Note that this method may not be able to return adouble NaN with exactly same bit pattern as thelong argument. IEEE 754 distinguishes between two kinds of NaNs, quiet NaNs andsignaling 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. SolongBitsToDouble may not be able to return adouble with a signaling NaN bit pattern. Consequently, for somelong values,doubleToRawLongBits(longBitsToDouble(start)) maynot equalstart. 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.

      Parameters:
      bits - anylong integer.
      Returns:
      thedouble floating-point value with the same bit pattern.

    • compareTo

      public int compareTo(Double anotherDouble)
      Compares twoDouble objects numerically. This method imposes a total order onDouble objects with two differences compared to the incomplete order defined by the Java language numerical comparison operators (<, <=, ==, >=, >) ondouble values.
      • A NaN isunordered with respect to other values and unequal to itself under the comparison operators. This method chooses to define Double.NaN to be equal to itself and greater than all otherdouble values (including Double.POSITIVE_INFINITY).
      • Positive zero and negative zero compare equal numerically, but are distinct and distinguishable values. This method chooses to define positive zero (+0.0d), to be greater than negative zero (-0.0d).
      This ensures that thenatural ordering ofDouble objects imposed by this method isconsistent with equals; seethis discussion for details of floating-point comparison and ordering.
      Specified by:
      compareTo in interface Comparable<Double>
      Parameters:
      anotherDouble - theDouble to be compared.
      Returns:
      the value0 ifanotherDouble is numerically equal to thisDouble; a value less than0 if thisDouble is numerically less thananotherDouble; and a value greater than0 if thisDouble is numerically greater thananotherDouble.
      SeeJava Language Specification:
      15.20.1 Numerical Comparison Operators<,<=,>, and>=
      Since:
      1.2

    • compare

      public static int compare(double d1, double d2)
      Compares the two specifieddouble values. The sign of the integer value returned is the same as that of the integer that would be returned by the call:
          Double.valueOf(d1).compareTo(Double.valueOf(d2))
      Parameters:
      d1 - the firstdouble to compare
      d2 - the seconddouble to compare
      Returns:
      the value0 ifd1 is numerically equal tod2; a value less than0 ifd1 is numerically less thand2; and a value greater than0 ifd1 is numerically greater thand2.
      Since:
      1.4

    • sum

      public static double sum(double a, double b)
      Adds twodouble values together as per the + operator.
      API Note:
      This method corresponds to the addition operation defined in IEEE 754.
      Parameters:
      a - the first operand
      b - the second operand
      Returns:
      the sum ofa andb
      SeeJava Language Specification:
      4.2.4 Floating-Point Operations
      Since:
      1.8
      See Also:

    • max

      public static double max(double a, double b)
      Returns the greater of twodouble values as if by callingMath.max.
      API Note:
      This method corresponds to the maximum operation defined in IEEE 754.
      Parameters:
      a - the first operand
      b - the second operand
      Returns:
      the greater ofa andb
      Since:
      1.8
      See Also:

    • min

      public static double min(double a, double b)
      Returns the smaller of twodouble values as if by callingMath.min.
      API Note:
      This method corresponds to the minimum operation defined in IEEE 754.
      Parameters:
      a - the first operand
      b - the second operand
      Returns:
      the smaller ofa andb.
      Since:
      1.8
      See Also:

    • describeConstable

      public Optional<Double> describeConstable()
      Returns anOptional containing the nominal descriptor for this instance, which is the instance itself.
      Specified by:
      describeConstable in interface Constable
      Returns:
      anOptional describing theDouble instance
      Since:
      12

    • resolveConstantDesc

      public Double resolveConstantDesc(MethodHandles.Lookup lookup)
      Resolves this instance as aConstantDesc, the result of which is the instance itself.
      Specified by:
      resolveConstantDesc in interface ConstantDesc
      Parameters:
      lookup - ignored
      Returns:
      theDouble instance
      Since:
      12