java.lang

Class Double

public final class Double extends Number implements Comparable<Double>

Instances of class Double represent primitive double values. Additionally, this class provides various helper functions and variables related to doubles.

Since: 1.0

UNKNOWN: partly updated to 1.5

Field Summary
static double	MAX_VALUE The maximum positive value a `double` may represent is 1.7976931348623157e+308.
static double	MIN_VALUE The minimum positive value a `double` may represent is 5e-324.
static double	NaN All IEEE 754 values of NaN have the same value in Java.
static double	NEGATIVE_INFINITY The value of a double representation -1.0/0.0, negative infinity.
static double	POSITIVE_INFINITY The value of a double representing 1.0/0.0, positive infinity.
static int	SIZE The number of bits needed to represent a `double`.
static Class<Double>	TYPE The primitive type `double` is represented by this `Class` object.

Constructor Summary
	Double(double value) Create a `Double` from the primitive `double` specified.
	Double(String s) Create a `Double` from the specified `String`.

Method Summary
byte	byteValue() Return the value of this `Double` as a `byte`.
static int	compare(double x, double y) Behaves like `new Double(x).compareTo(new Double(y))`; in other words this compares two doubles, special casing NaN and zero, without the overhead of objects.
int	compareTo(Double d) Compare two Doubles numerically by comparing their `double` values.
static long	doubleToLongBits(double value) Convert the double to the IEEE 754 floating-point "double format" bit layout.
static long	doubleToRawLongBits(double value) Convert the double to the IEEE 754 floating-point "double format" bit layout.
double	doubleValue() Return the value of this `Double`.
boolean	equals(Object obj) Returns `true` if `obj` is an instance of `Double` and represents the same double value.
float	floatValue() Return the value of this `Double` as a `float`.
int	hashCode() Return a hashcode representing this Object.
int	intValue() Return the value of this `Double` as an `int`.
static boolean	isInfinite(double v) Return `true` if the `double` has a value equal to either `NEGATIVE_INFINITY` or `POSITIVE_INFINITY`, otherwise return `false`.
boolean	isInfinite() Return `true` if the value of this `Double` is the same as `NEGATIVE_INFINITY` or `POSITIVE_INFINITY`, otherwise return `false`.
static boolean	isNaN(double v) Return `true` if the `double` has the same value as `NaN`, otherwise return `false`.
boolean	isNaN() Return `true` if the value of this `Double` is the same as `NaN`, otherwise return `false`.
static double	longBitsToDouble(long bits) Convert the argument in IEEE 754 floating-point "double format" bit layout to the corresponding float.
long	longValue() Return the value of this `Double` as a `long`.
static double	parseDouble(String str) Parse the specified `String` as a `double`.
short	shortValue() Return the value of this `Double` as a `short`.
static String	toHexString(double d) Convert a double value to a hexadecimal string.
static String	toString(double d) Convert the `double` to a `String`.
String	toString() Convert the `double` value of this `Double` to a `String`.
static Double	valueOf(double val) Returns a `Double` object wrapping the value.
static Double	valueOf(String s) Create a new `Double` object using the `String`.

Field Detail

MAX_VALUE

public static final double MAX_VALUE

The maximum positive value a double may represent is 1.7976931348623157e+308.

MIN_VALUE

public static final double MIN_VALUE

The minimum positive value a double may represent is 5e-324.

NaN

public static final double NaN

All IEEE 754 values of NaN have the same value in Java.

NEGATIVE_INFINITY

public static final double NEGATIVE_INFINITY

The value of a double representation -1.0/0.0, negative infinity.

POSITIVE_INFINITY

public static final double POSITIVE_INFINITY

The value of a double representing 1.0/0.0, positive infinity.

SIZE

public static final int SIZE

The number of bits needed to represent a double.

Since: 1.5

TYPE

public static final Class<Double> TYPE

The primitive type double is represented by this Class object.

Since: 1.1

Constructor Detail

Double

public Double(double value)

Create a Double from the primitive double specified.

Parameters: value the double argument

Double

public Double(String s)

Create a Double from the specified String. This method calls Double.parseDouble().

Parameters: s the String to convert

Throws: NumberFormatException if s cannot be parsed as a double NullPointerException if s is null

Method Detail

byteValue

public byte byteValue()

Return the value of this Double as a byte.

Returns: the byte value

Since: 1.1

compare

public static int compare(double x, double y)

Behaves like new Double(x).compareTo(new Double(y)); in other words this compares two doubles, special casing NaN and zero, without the overhead of objects.

Parameters: x the first double to compare y the second double to compare

Returns: the comparison

Since: 1.4

Compare two Doubles numerically by comparing their double values. The result is positive if the first is greater, negative if the second is greater, and 0 if the two are equal. However, this special cases NaN and signed zero as follows: NaN is considered greater than all other doubles, including POSITIVE_INFINITY, and positive zero is considered greater than negative zero.

Parameters: d the Double to compare

Returns: the comparison

Since: 1.2

doubleToLongBits

public static long doubleToLongBits(double value)

Convert the double to the IEEE 754 floating-point "double format" bit layout. Bit 63 (the most significant) is the sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa. This function collapses all versions of NaN to 0x7ff8000000000000L. The result of this function can be used as the argument to Double.longBitsToDouble(long) to obtain the original double value.

Parameters: value the double to convert

Returns: the bits of the double

See Also: Double

doubleToRawLongBits

public static long doubleToRawLongBits(double value)

Convert the double to the IEEE 754 floating-point "double format" bit layout. Bit 63 (the most significant) is the sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa. This function leaves NaN alone, rather than collapsing to a canonical value. The result of this function can be used as the argument to Double.longBitsToDouble(long) to obtain the original double value.

Parameters: value the double to convert

Returns: the bits of the double

See Also: Double

doubleValue

public double doubleValue()

Return the value of this Double.

Returns: the double value

equals

public boolean equals(Object obj)

Returns true if obj is an instance of Double and represents the same double value. Unlike comparing two doubles with ==, this treats two instances of Double.NaN as equal, but treats 0.0 and -0.0 as unequal.

Note that d1.equals(d2) is identical to doubleToLongBits(d1.doubleValue()) == doubleToLongBits(d2.doubleValue()).

Parameters: obj the object to compare

Returns: whether the objects are semantically equal

floatValue

public float floatValue()

Return the value of this Double as a float.

Returns: the float value

hashCode

public int hashCode()

Return a hashcode representing this Object. Double's hash code is calculated by:

long v = Double.doubleToLongBits(doubleValue());

    int hash = (int)(v^(v>>32))

Returns: this Object's hash code

See Also: Double

intValue

public int intValue()

Return the value of this Double as an int.

Returns: the int value

isInfinite

public static boolean isInfinite(double v)

Return true if the double has a value equal to either NEGATIVE_INFINITY or POSITIVE_INFINITY, otherwise return false.

Parameters: v the double to compare

Returns: whether the argument is (-/+) infinity.

isInfinite

public boolean isInfinite()

Return true if the value of this Double is the same as NEGATIVE_INFINITY or POSITIVE_INFINITY, otherwise return false.

Returns: whether this Double is (-/+) infinity

isNaN

public static boolean isNaN(double v)

Return true if the double has the same value as NaN, otherwise return false.

Parameters: v the double to compare

Returns: whether the argument is NaN.

isNaN

public boolean isNaN()

Return true if the value of this Double is the same as NaN, otherwise return false.

Returns: whether this Double is NaN

longBitsToDouble

public static double longBitsToDouble(long bits)

Convert the argument in IEEE 754 floating-point "double format" bit layout to the corresponding float. Bit 63 (the most significant) is the sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa. This function leaves NaN alone, so that you can recover the bit pattern with Double.doubleToRawLongBits(double).

Parameters: bits the bits to convert

Returns: the double represented by the bits

longValue

public long longValue()

Return the value of this Double as a long.

Returns: the long value

parseDouble

public static double parseDouble(String str)

Parse the specified String as a double. The extended BNF grammar is as follows:

 DecodableString:
      ( [ - | + ] NaN )
    | ( [ - | + ] Infinity )
    | ( [ - | + ] FloatingPoint
              [ f | F | d
                | D] )
 FloatingPoint:
      ( { Digit }+ [ . { Digit } ]
              [ Exponent ] )
    | ( . { Digit }+ [ Exponent ] )
 Exponent:
      ( ( e | E )
              [ - | + ] { Digit }+ )
 Digit: '0' through '9'

NaN and infinity are special cases, to allow parsing of the output of toString. Otherwise, the result is determined by calculating n * 10^exponent to infinite precision, then rounding to the nearest double. Remember that many numbers cannot be precisely represented in floating point. In case of overflow, infinity is used, and in case of underflow, signed zero is used. Unlike Integer.parseInt, this does not accept Unicode digits outside the ASCII range.

If an unexpected character is found in the String, a NumberFormatException will be thrown. Leading and trailing 'whitespace' is ignored via String.trim(), but spaces internal to the actual number are not allowed.

To parse numbers according to another format, consider using {@link java.text.NumberFormat}.

Parameters: str the String to convert

Returns: the double value of s

Throws: NumberFormatException if s cannot be parsed as a double NullPointerException if s is null

Since: 1.2

UNKNOWN: specify where/how we are not in accord with the spec.

shortValue

public short shortValue()

Return the value of this Double as a short.

Returns: the short value

Since: 1.1

toHexString

public static String toHexString(double d)

Convert a double value to a hexadecimal string. This converts as follows:

A NaN value is converted to the string "NaN".
Positive infinity is converted to the string "Infinity".
Negative infinity is converted to the string "-Infinity".
For all other values, the first character of the result is '-' if the value is negative. This is followed by '0x1.' if the value is normal, and '0x0.' if the value is denormal. This is then followed by a (lower-case) hexadecimal representation of the mantissa, with leading zeros as required for denormal values. The next character is a 'p', and this is followed by a decimal representation of the unbiased exponent.

Parameters: d the double value

Returns: the hexadecimal string representation

Since: 1.5

toString

public static String toString(double d)

Convert the double to a String. Floating-point string representation is fairly complex: here is a rundown of the possible values. "[-]" indicates that a negative sign will be printed if the value (or exponent) is negative. "<number>" means a string of digits ('0' to '9'). "<digit>" means a single digit ('0' to '9').

Value of Double	String Representation
[+-] 0	`[-]0.0`
Between [+-] 10^-3 and 10⁷, exclusive	`[-]number.number`
Other numeric value	`[-]<digit>.<number> E[-]<number>`
[+-] infinity	`[-]Infinity`
NaN	`NaN`

Yes, negative zero is a possible value. Note that there is always a . and at least one digit printed after it: even if the number is 3, it will be printed as 3.0. After the ".", all digits will be printed except trailing zeros. The result is rounded to the shortest decimal number which will parse back to the same double.

To create other output formats, use {@link java.text.NumberFormat}.

Parameters: d the double to convert

Returns: the String representing the double

UNKNOWN: specify where we are not in accord with the spec.

toString

public String toString()

Convert the double value of this Double to a String. This method calls Double.toString(double) to do its dirty work.

Returns: the String representation

See Also: Double

valueOf

public static Double valueOf(double val)

Returns a Double object wrapping the value. In contrast to the Double constructor, this method may cache some values. It is used by boxing conversion.

Parameters: val the value to wrap

Returns: the Double

Since: 1.5

valueOf

public static Double valueOf(String s)

Create a new Double object using the String.

Parameters: s the String to convert

Returns: the new Double

Throws: NumberFormatException if s cannot be parsed as a double NullPointerException if s is null.