Class Double

Method Details

• toString

  public static String toString(double d)

  Returns a string representation of the double argument. All characters mentioned below are ASCII characters.

  • If the argument is NaN, the result is the string "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 magnitude m:
    • If m is infinity, it is represented by the characters "Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity".
    • If m is zero, it is represented by the characters "0.0"; thus, negative zero produces the result "-0.0" and positive zero produces the result "0.0".
    • Otherwise m is positive and finite. It is converted to a string in two stages:
      • Selection of a decimal: A well-defined decimal d_m is selected to represent m. This decimal is (almost always) the shortest one that rounds to m according to the round to nearest rounding policy of IEEE 754 floating-point arithmetic.
      • Formatting as a string: The decimal d_m is formatted as a string, either in plain or in computerized scientific notation, depending on its value.

  A decimal is a number of the form s×10ⁱ for some (unique) integers s > 0 and i such that s is not a multiple of 10. These integers are the significand and the exponent, respectively, of the decimal. The length of the decimal is the (unique) positive integer n meeting 10^n-1 ≤ s < 10ⁿ.

  The decimal d_m for a finite positive m is defined as follows:

  • Let R be the set of all decimals that round to m according to the usual round to nearest rounding policy of IEEE 754 floating-point arithmetic.
  • Let p be the minimal length over all decimals in R.
  • When p ≥ 2, let T be the set of all decimals in R with length p. Otherwise, let T be the set of all decimals in R with length 1 or 2.
  • Define d_m as the decimal in T that is closest to m. Or if there are two such decimals in T, select the one with the even significand.

  The (uniquely) selected decimal d_m is then formatted. Let s, i and n be the significand, exponent and length of d_m, respectively. Further, let e = n + i - 1 and let s₁…s_n be the usual decimal expansion of s. Note that s₁ ≠ 0 and s_n ≠ 0. Below, the decimal point '.' is '\u002E' and the exponent indicator 'E' is '\u0045'.

  • Case -3 ≤ e < 0: d_m is formatted as 0.0…0s₁…s_n, where there are exactly -(n + i) zeroes between the decimal point and s₁. For example, 123 × 10^-4 is formatted as 0.0123.
  • Case 0 ≤ e < 7:
    • Subcase i ≥ 0: d_m is formatted as s₁…s_n0…0.0, where there are exactly i zeroes between s_n and the decimal point. For example, 123 × 10² is formatted as 12300.0.
    • Subcase i < 0: d_m is formatted as s₁…s_n+i.s_n+i+1…s_n, where there are exactly -i digits to the right of the decimal point. For example, 123 × 10^-1 is formatted as 12.3.
  • Case e < -3 or e ≥ 7: computerized scientific notation is used to format d_m. Here e is formatted as by Integer.toString(int).
    • Subcase n = 1: d_m is formatted as s₁.0Ee. For example, 1 × 10²³ is formatted as 1.0E23.
    • Subcase n > 1: d_m is formatted as s₁.s₂…s_nEe. For example, 123 × 10^-21 is formatted as 1.23E-19.

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

  Parameters:

  d - the double to be converted.

  Returns:

  a string representation of the argument.

• toHexString

  public static String toHexString(double d)

  Returns a hexadecimal string representation of the double argument. All characters mentioned below are ASCII characters.

  • If the argument is NaN, the result is the string "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 magnitude m:
    • If m is infinity, it is represented by the string "Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity".
    • If m is zero, it is represented by the string "0x0.0p0"; thus, negative zero produces the result "-0x0.0p0" and positive zero produces the result "0x0.0p0".
    • If m is a double value with a normalized representation, substrings are used to represent the significand and exponent fields. The significand is represented by the characters "0x1." followed by a lowercase hexadecimal representation of the rest of the significand as a fraction. Trailing zeros in the hexadecimal representation are removed unless all the digits are zero, in which case a single zero is used. Next, the exponent is represented by "p" followed by a decimal string of the unbiased exponent as if produced by a call to Integer.toString on the exponent value.
    • If m is a double value with a subnormal representation, the significand is represented by the characters "0x0." followed by a hexadecimal representation of the rest of the significand as a 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 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

  Parameters:

  d - the double to be converted.

  Returns:

  a hex string representation of the argument.

  Since:

  1.5

• valueOf

  public static Double valueOf(String s) throws NumberFormatException

  Returns a Double object holding the double value represented by the argument string s.

  If s is null, then a NullPointerException is thrown.

  Leading and trailing whitespace characters in s are ignored. Whitespace is removed as if by the String.trim() method; that is, both ASCII space and control characters are removed. The rest of s should constitute a FloatValue as described by the lexical syntax rules:

  FloatValue:

  Sign_opt NaN

  Sign_opt Infinity

  Sign_opt FloatingPointLiteral

  Sign_opt HexFloatingPointLiteral

  SignedInteger

  HexFloatingPointLiteral:

  HexSignificand BinaryExponent FloatTypeSuffix_opt

  HexSignificand:

  HexNumeral

  HexNumeral .

  0x HexDigits_opt . HexDigits

  0X HexDigits_opt . HexDigits

  BinaryExponent:

  BinaryExponentIndicator SignedInteger

  BinaryExponentIndicator:

  p

  P

  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.

  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:

  Copy

   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
   }
  

  Parameters:

  s - the string to be parsed.

  Returns:

  a Double object holding the value represented by the String argument.

  Throws:

  NumberFormatException - if the string does not contain a parsable number.

• valueOf

  public static Double valueOf(double d)

  Returns a Double instance representing the specified double value. If a new Double instance is not required, this method should generally be used in preference to the constructor Double(double), as this method is likely to yield significantly better space and time performance by caching frequently requested values.

  Parameters:

  d - a double value.

  Returns:

  a Double instance representing d.

  Since:

  1.5

• parseDouble

  public static double parseDouble(String s) throws NumberFormatException

  Returns a new double initialized to the value represented by the specified String, as performed by the valueOf method of class Double.

  Parameters:

  s - the string to be parsed.

  Returns:

  the double value represented by the string argument.

  Throws:

  NullPointerException - if the string is null

  NumberFormatException - if the string does not contain a parsable double.

  Since:

  1.2

  See Also:

  • valueOf(String)

• isNaN

  public static boolean isNaN(double v)

  Returns true 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)

  Returns true 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)

  Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).

  API Note:

  This method corresponds to the isFinite operation defined in IEEE 754.

  Parameters:

  d - the double value to be tested

  Returns:

  true if the argument is a finite floating-point value, false otherwise.

  Since:

  1.8

• isNaN

  public boolean isNaN()

  Returns true if this Double value is a Not-a-Number (NaN), false otherwise.

  Returns:

  true if the value represented by this object is NaN; false otherwise.

• isInfinite

  public boolean isInfinite()

  Returns true if this Double value is infinitely large in magnitude, false otherwise.

  Returns:

  true if the value represented by this object is positive infinity or negative infinity; false otherwise.

• toString

  public String toString()

  Returns a string representation of this Double object. The primitive double value represented by this object is converted to a string exactly as if by the method toString of one argument.

  Overrides:

  toString in class Object

  Returns:

  a String representation of this object.

  See Also:

  • toString(double)

• byteValue

  public byte byteValue()

  Returns the value of this Double as a byte after a narrowing primitive conversion.

  Overrides:

  byteValue in class Number

  Returns:

  the double value represented by this object converted to type byte

  See Java Language Specification:

  5.1.3 Narrowing Primitive Conversion
  

  Since:

  1.1

• shortValue

  public short shortValue()

  Returns the value of this Double as a short after a narrowing primitive conversion.

  Overrides:

  shortValue in class Number

  Returns:

  the double value represented by this object converted to type short

  See Java Language Specification:

  5.1.3 Narrowing Primitive Conversion
  

  Since:

  1.1

• intValue

  public int intValue()

  Returns the value of this Double as an int after a narrowing primitive conversion.

  Specified by:

  intValue in class Number

  Returns:

  the double value represented by this object converted to type int

  See Java Language Specification:

  5.1.3 Narrowing Primitive Conversion
  

• longValue

  public long longValue()

  Returns the value of this Double as a long after a narrowing primitive conversion.

  Specified by:

  longValue in class Number

  Returns:

  the double value represented by this object converted to type long

  See Java Language Specification:

  5.1.3 Narrowing Primitive Conversion
  

• floatValue

  public float floatValue()

  Returns the value of this Double as a float 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:

  the double value represented by this object converted to type float

  See Java Language Specification:

  5.1.3 Narrowing Primitive Conversion
  

  Since:

  1.0

• doubleValue

  public double doubleValue()

  Returns the double value of this Double object.

  Specified by:

  doubleValue in class Number

  Returns:

  the double value represented by this object

• hashCode

  public int hashCode()

  Returns a hash code for this Double object. The result is the exclusive OR of the two halves of the long integer bit representation, exactly as produced by the method 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());

  Overrides:

  hashCode in class Object

  Returns:

  a hash code value for this object.

  See Also:

  • Object.equals(java.lang.Object)
  • System.identityHashCode(java.lang.Object)

• hashCode

  public static int hashCode(double value)

  Returns a hash code for a double value; compatible with Double.hashCode().

  Parameters:

  value - the value to hash

  Returns:

  a hash code value for a double value.

  Since:

  1.8

• equals

  public boolean equals(Object obj)

  Compares this object against the specified object. The result is true if and only if the argument is not null and is a Double object that represents a double that has the same value as the double represented by this object. For this purpose, two double values are considered to be the same if and only if the method doubleToLongBits(double) returns the identical long value when applied to each.

  Overrides:

  equals in class Object

  API Note:

  This method is defined in terms of doubleToLongBits(double) rather than the == operator on double values since the == operator does not define an equivalence relation and to satisfy the equals contract an equivalence relation must be implemented; see this 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.

  See Java Language Specification:

  15.21.1 Numerical Equality Operators == and !=
  

  See Also:

  • doubleToLongBits(double)

• doubleToLongBits

  public static long doubleToLongBits(double value)

  Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout.

  Bit 63 (the bit that is selected by the mask 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).

  Parameters:

  value - a double precision floating-point number.

  Returns:

  the bits that represent the floating-point number.

• doubleToRawLongBits

  public static long doubleToRawLongBits(double value)

  Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout, preserving Not-a-Number (NaN) values.

  Bit 63 (the bit that is selected by the mask 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.

  Parameters:

  value - a double precision floating-point number.

  Returns:

  the bits that represent the floating-point number.

  Since:

  1.3

• longBitsToDouble

  public static double longBitsToDouble(long bits)

  Returns the double value corresponding to a given bit representation. The argument is considered to be a representation of a floating-point value according to the IEEE 754 floating-point "double format" bit layout.

  If the argument is 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:

  Copy

  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·2^e-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.

  Parameters:

  bits - any long integer.

  Returns:

  the double floating-point value with the same bit pattern.

• compareTo

  public int compareTo(Double anotherDouble)

  Compares two Double objects numerically. This method imposes a total order on Double objects with two differences compared to the incomplete order defined by the Java language numerical comparison operators (<, <=, ==, >=, >) on double values.

  • A NaN is unordered 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 other double 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 the natural ordering of Double objects imposed by this method is consistent with equals; see this discussion for details of floating-point comparison and ordering.

  Specified by:

  compareTo in interface Comparable<Double>

  Parameters:

  anotherDouble - the Double to be compared.

  Returns:

  the value 0 if anotherDouble is numerically equal to this Double; a value less than 0 if this Double is numerically less than anotherDouble; and a value greater than 0 if this Double is numerically greater than anotherDouble.

  See Java Language Specification:

  15.20.1 Numerical Comparison Operators <, <=, >, and >=
  

  Since:

  1.2

• compare

  public static int compare(double d1, double d2)

  Compares the two specified double values. The sign of the integer value returned is the same as that of the integer that would be returned by the call:

      Double.valueOf(d1).compareTo(Double.valueOf(d2))
   

  Parameters:

  d1 - the first double to compare

  d2 - the second double to compare

  Returns:

  the value 0 if d1 is numerically equal to d2; a value less than 0 if d1 is numerically less than d2; and a value greater than 0 if d1 is numerically greater than d2.

  Since:

  1.4

• sum

  public static double sum(double a, double b)

  Adds two double 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 of a and b

  See Java Language Specification:

  4.2.4 Floating-Point Operations
  

  Since:

  1.8

  See Also:

  • BinaryOperator

• max

  public static double max(double a, double b)

  Returns the greater of two double values as if by calling Math.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 of a and b

  Since:

  1.8

  See Also:

  • BinaryOperator

• min

  public static double min(double a, double b)

  Returns the smaller of two double values as if by calling Math.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 of a and b.

  Since:

  1.8

  See Also:

  • BinaryOperator

• describeConstable

  public Optional<Double> describeConstable()

  Returns an Optional containing the nominal descriptor for this instance, which is the instance itself.

  Specified by:

  describeConstable in interface Constable

  Returns:

  an Optional describing the Double instance

  Since:

  12

• resolveConstantDesc

  public Double resolveConstantDesc(MethodHandles.Lookup lookup)

  Resolves this instance as a ConstantDesc, the result of which is the instance itself.

  Specified by:

  resolveConstantDesc in interface ConstantDesc

  Parameters:

  lookup - ignored

  Returns:

  the Double instance

  Since:

  12