Class: java.lang.Double

The Double class wraps a value of the primitive type double in an object. An object of type Double contains a single field whose type is double.

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

Authors:
@author Lee Boynton
@author Arthur van Hoff
@author Joseph D. Darcy
Since:
@since JDK1.0

Inheritance

Superclass tree: Implements:

Methods

  • Doubletop

    public Double(double value)
    Constructs a newly allocated Double object that represents the primitive double argument.
    Parameters:
    @param value the value to be represented by the Double .
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  • Doubletop

    public Double(String s) throws NumberFormatException
    Constructs a newly allocated Double object that represents the floating-point value of type double represented by the string. The string is converted to a double value as if by the valueOf method.
    Parameters:
    @param s a string to be converted to a Double .
    Exceptions:
    @throws NumberFormatException if the string does not contain a parsable number.
    See:
    @see Double.valueOf(java.lang.String)
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  • byteValuetop

    public byte byteValue()
    Returns the value of this Double as a byte (by casting to a byte).
    Return:
    @return the double value represented by this object converted to type byte
    Since:
    @since JDK1.1
    Override hierarchy:
    byteValue from Number
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  • comparetop

    public static int compare(double d1, double d2)
    Compares the two specified double values. The sign of the integer value returned is the same as that of the integer that would be returned by the call: 
        new Double(d1).compareTo(new Double(d2))
    Parameters:
    @param d1 the first double to compare
    @param d2 the second double to compare
    Return:
    @return 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:
    @since 1.4
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  • compareTotop

    public int compareTo(Double anotherDouble)
    Compares two Double objects numerically. There are two ways in which comparisons performed by this method differ from those performed by the Java language numerical comparison operators (<, <=, ==, >=, >) when applied to primitive double values:
    • Double.NaN is considered by this method to be equal to itself and greater than all other double values (including Double.POSITIVE_INFINITY).
    • 0.0d is considered by this method to be greater than -0.0d.
    This ensures that the natural ordering of Double objects imposed by this method is consistent with equals.
    Parameters:
    @param anotherDouble the Double to be compared.
    Return:
    @return the value 0 if anotherDouble is numerically equal to this Double ; a value less than 0 if this Double is numerically less than anotherDouble ; and a value greater than 0 if this Double is numerically greater than anotherDouble .
    Since:
    @since 1.2
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  • doubleToLongBitstop

    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 Double.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:
    @param value a double precision floating-point number.
    Return:
    @return the bits that represent the floating-point number.
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  • doubleToRawLongBitstop

    public static native 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 Double.longBitsToDouble(long) method, will produce a floating-point value the same as the argument to doubleToRawLongBits.

    Parameters:
    @param value a double precision floating-point number.
    Return:
    @return the bits that represent the floating-point number.
    Since:
    @since 1.3
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  • doubleValuetop

    public double doubleValue()
    Returns the double value of this Double object.
    Return:
    @return the double value represented by this object
    Override hierarchy:
    doubleValue from Number
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  • equalstop

    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 Double.doubleToLongBits(double) returns the identical long value when applied to each.

    Note that in most cases, for two instances of class Double, d1 and d2, the value of d1.equals(d2) is true if and only if

    d1.doubleValue() == d2.doubleValue()

    also has the value true. However, there are two exceptions:

    • If d1 and d2 both represent Double.NaN, then the equals method returns true, even though Double.NaN==Double.NaN has the value false.
    • If d1 represents +0.0 while d2 represents -0.0, or vice versa, the equal test has the value false, even though +0.0==-0.0 has the value true.
    This definition allows hash tables to operate properly.
    Parameters:
    @param obj the object to compare with.
    Return:
    @return true if the objects are the same; false otherwise.
    See:
    @see Double.doubleToLongBits(double)
    Override hierarchy:
    equals from Object
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  • floatValuetop

    public float floatValue()
    Returns the float value of this Double object.
    Return:
    @return the double value represented by this object converted to type float
    Since:
    @since JDK1.0
    Override hierarchy:
    floatValue from Number
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  • hashCodetop

    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 Double.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());
    Return:
    @return a hash code value for this object.
    Override hierarchy:
    hashCode from Object
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  • intValuetop

    public int intValue()
    Returns the value of this Double as an int (by casting to type int).
    Return:
    @return the double value represented by this object converted to type int
    Override hierarchy:
    intValue from Number
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  • isInfinitetop

    public boolean isInfinite()
    Returns true if this Double value is infinitely large in magnitude, false otherwise.
    Return:
    @return true if the value represented by this object is positive infinity or negative infinity; false otherwise.
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  • isInfinitetop

    public static boolean isInfinite(double v)
    Returns true if the specified number is infinitely large in magnitude, false otherwise.
    Parameters:
    @param v the value to be tested.
    Return:
    @return true if the value of the argument is positive infinity or negative infinity; false otherwise.
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  • isNaNtop

    public boolean isNaN()
    Returns true if this Double value is a Not-a-Number (NaN), false otherwise.
    Return:
    @return true if the value represented by this object is NaN; false otherwise.
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  • isNaNtop

    public static boolean isNaN(double v)
    Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
    Parameters:
    @param v the value to be tested.
    Return:
    @return true if the value of the argument is NaN; false otherwise.
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  • longBitsToDoubletop

    public static native 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: 

     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.

    Parameters:
    @param bits any long integer.
    Return:
    @return the double floating-point value with the same bit pattern.
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  • longValuetop

    public long longValue()
    Returns the value of this Double as a long (by casting to type long).
    Return:
    @return the double value represented by this object converted to type long
    Override hierarchy:
    longValue from Number
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  • parseDoubletop

    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:
    @param s the string to be parsed.
    Return:
    @return the double value represented by the string argument.
    Exceptions:
    @throws NumberFormatException if the string does not contain a parsable double .
    See:
    @see Double.valueOf(java.lang.String)
    Since:
    @since 1.2
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  • shortValuetop

    public short shortValue()
    Returns the value of this Double as a short (by casting to a short).
    Return:
    @return the double value represented by this object converted to type short
    Since:
    @since JDK1.1
    Override hierarchy:
    shortValue from Number
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  • toHexStringtop

    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 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
    Parameters:
    @param d the double to be converted.
    Return:
    @return a hex string representation of the argument.
    Since:
    @since 1.5
    Misc:
    @author Joseph D. Darcy
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  • toStringtop

    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.
    Return:
    @return a String representation of this object.
    See:
    @see Double.toString(double)
    Override hierarchy:
    toString from Object
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  • toStringtop

    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".
      • If m is greater than or equal to 10-3 but less than 107, then it is represented as the integer part of m, in decimal form with no leading zeroes, followed by '.' ('\u002E'), followed by one or more decimal digits representing the fractional part of m.
      • If m is less than 10-3 or greater than or equal to 107, then it is represented in so-called "computerized scientific notation." Let n be the unique integer such that 10n ≤ m {@literal <_ _10sup="_10sup">n+1; then let a be the mathematically exact quotient of m and 10n so that 1 ≤ a {@literal <_ _10.="_10." the="the" magnitude="magnitude" is="is" then="then" represented="represented" as="as" integer="integer" part="part" of="of" i="i">a, as a single decimal digit, followed by '.' ('\u002E'), followed by decimal digits representing the fractional part of a, followed by the letter 'E' ('\u0045'), followed by a representation of n as a decimal integer, as produced by the method Integer.toString(int).
    How many digits must be printed for the fractional part of m or a? There must be at least one digit to represent the fractional part, and beyond that as many, but only as many, more digits as are needed to uniquely distinguish the argument value from adjacent values of type double. That is, suppose that x is the exact mathematical value represented by the decimal representation produced by this method for a finite nonzero argument d. Then d must be the double value nearest to x; or if two double values are equally close to x, then d must be one of them and the least significant bit of the significand of d must be 0.

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

    Parameters:
    @param d the double to be converted.
    Return:
    @return a string representation of the argument.
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  • valueOftop

    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(double), as this method is likely to yield significantly better space and time performance by caching frequently requested values.
    Parameters:
    @param d a double value.
    Return:
    @return a Double instance representing d .
    Since:
    @since 1.5
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  • valueOftop

    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:
    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
    where Sign, FloatingPointLiteral, HexNumeral, HexDigits, SignedInteger and FloatTypeSuffix are as defined in the lexical structure sections of the Java Language Specification. If s does not have the form of a FloatValue, then a NumberFormatException is thrown. Otherwise, s is regarded as representing an exact decimal value in the usual "computerized scientific notation" or as an exact 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. Finally, a Double object representing this double value is returned.

    To interpret localized string representations of a floating-point value, use subclasses of java.text.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 the Java Language Specification, 2nd
       // edition, section 3.10.2.

       // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
       "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+

       // . Digits ExponentPart_opt FloatTypeSuffix_opt
       "(\\.("+Digits+")("+Exp+")?)|"+

       // Hexadecimal strings
       "((" +
        // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
        "(0[xX]" + HexDigits + "(\\.)?)|" +

        // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +

        ")[pP][+-]?" + Digits + "))" +
       "[fFdD]?))" +
       "[\\x00-\\x20]*");// Optional trailing "whitespace"

  if (Pattern.matches(fpRegex, myString))
      Double.valueOf(myString); // Will not throw NumberFormatException
  else {
      // Perform suitable alternative action
  }
    Parameters:
    @param s the string to be parsed.
    Return:
    @return a Double object holding the value represented by the String argument.
    Exceptions:
    @throws NumberFormatException if the string does not contain a parsable number.
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Fields

  • MAX_EXPONENT

    public static final int MAX_EXPONENT = 1023
    Maximum exponent a finite double variable may have. It is equal to the value returned by Math.getExponent(Double.MAX_VALUE).

  • MAX_VALUE

    public static final double MAX_VALUE = 1.7976931348623157E308
    A constant holding the largest positive finite value of type double, (2-2-52)·21023. It is equal to the hexadecimal floating-point literal 0x1.fffffffffffffP+1023 and also equal to Double.longBitsToDouble(0x7fefffffffffffffL).

  • MIN_EXPONENT

    public static final int MIN_EXPONENT = -1022
    Minimum exponent a normalized double variable may have. It is equal to the value returned by Math.getExponent(Double.MIN_NORMAL).

  • MIN_NORMAL

    public static final double MIN_NORMAL = 2.2250738585072014E-308
    A constant holding the smallest positive normal value of type double, 2-1022. It is equal to the hexadecimal floating-point literal 0x1.0p-1022 and also equal to Double.longBitsToDouble(0x0010000000000000L).

  • MIN_VALUE

    public static final double MIN_VALUE = 4.9E-324
    A constant holding the smallest positive nonzero value of type double, 2-1074. It is equal to the hexadecimal floating-point literal 0x0.0000000000001P-1022 and also equal to Double.longBitsToDouble(0x1L).

  • NEGATIVE_INFINITY

    public static final double NEGATIVE_INFINITY = -Infinity
    A constant holding the negative infinity of type double. It is equal to the value returned by Double.longBitsToDouble(0xfff0000000000000L).

  • NaN

    public static final double NaN = NaN
    A constant holding a Not-a-Number (NaN) value of type double. It is equivalent to the value returned by Double.longBitsToDouble(0x7ff8000000000000L).

  • POSITIVE_INFINITY

    public static final double POSITIVE_INFINITY = Infinity
    A constant holding the positive infinity of type double. It is equal to the value returned by Double.longBitsToDouble(0x7ff0000000000000L).

  • SIZE

    public static final int SIZE = 64
    The number of bits used to represent a double value.

  • TYPE

    public static final Class<Double> TYPE
    The Class instance representing the primitive type double.