Added in API level 1

Double

class Double : Number, Comparable<Double!>

kotlin.Any
↳	kotlin.Number
	↳	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.

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 and negative infinity), and NaN (not-a-number).

An equivalence relation on a set of values is a boolean relation on pairs of values that is reflexive, symmetric, and transitive. For more discussion of equivalence relations and object equality, see the Object.equals specification. An equivalence relation partitions the values it operates over into sets called equivalence classes. All the members of the equivalence class are equal to each other under the relation. An equivalence class may contain only a single member. At least for some purposes, all the members of an equivalence class are substitutable for each other. In particular, in a numeric expression equivalent values can be substituted for one another without changing the result of the expression, meaning changing the equivalence class of the result of the expression.

Notably, the built-in == operation on floating-point values is not an equivalence relation. Despite not defining an equivalence relation, the semantics of the IEEE 754 == operator were deliberately designed to meet other needs of numerical computation. There are two exceptions where the properties of an equivalence relation are not satisfied by == on floating-point values:

• If v1 and v2 are both NaN, then v1 == v2 has the value false. Therefore, for two NaN arguments the reflexive property of an equivalence relation is not satisfied by the == operator.
• If v1 represents +0.0 while v2 represents -0.0, or vice versa, then v1 == v2 has the value true even though +0.0 and -0.0 are distinguishable under various floating-point operations. For example, 1.0/+0.0 evaluates to positive infinity while 1.0/-0.0 evaluates to negative 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 the trichotomy of comparison does not hold.

To provide the appropriate semantics for equals and compareTo methods, those methods cannot simply be wrappers around == or ordered comparison operations. Instead, equals defines NaN arguments to be equal to each other and defines +0.0 to not be equal to -0.0, restoring reflexivity. For comparisons, compareTo defines a total order where -0.0 is less than +0.0 and where a NaN is equal to itself and considered greater than positive infinity.

The operational semantics of equals and compareTo are expressed in terms of bit-wise converting the floating-point values to integral values.

The natural ordering implemented by compareTo is consistent with equals. That is, two objects are reported as equal by equals if and only if compareTo on those objects returns zero.

The adjusted behaviors defined for equals and compareTo allow instances of wrapper classes to work properly with conventional data structures. For example, defining NaN values to be equals to one another allows NaN to be used as an element of a HashSet or as the key of a HashMap. Similarly, defining compareTo as a total ordering, including +0.0, -0.0, and NaN, allows instances of wrapper classes to be used as elements of a SortedSet or as keys of a SortedMap.

Summary

Constants
static Int	BYTES The number of bytes used to represent a double value.
static Int	MAX_EXPONENT Maximum exponent a finite double variable may have.
static Double	MAX_VALUE A constant holding the largest positive finite value of type double, (2-2-52)·21023.
static Int	MIN_EXPONENT Minimum exponent a normalized double variable may have.
static Double	MIN_NORMAL A constant holding the smallest positive normal value of type double, 2-1022.
static Double	MIN_VALUE A constant holding the smallest positive nonzero value of type double, 2-1074.
static Double	NEGATIVE_INFINITY A constant holding the negative infinity of type double.
static Double	NaN A constant holding a Not-a-Number (NaN) value of type double.
static Double	POSITIVE_INFINITY A constant holding the positive infinity of type double.
static Int	PRECISION The number of bits in the significand of a double value.
static Int	SIZE The number of bits used to represent a double value.

Public constructors
Double(value: Double) Constructs a newly allocated Double object that represents the primitive double argument.
Double(s: String) Constructs a newly allocated Double object that represents the floating-point value of type double represented by the string.

Public methods
static Int	compare(d1: Double, d2: Double) Compares the two specified double values.
Int	compareTo(other: Double) Compares two Double objects numerically.
static Long	doubleToLongBits(value: Double) Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout.
static Long	doubleToRawLongBits(value: Double) 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.
Boolean	equals(other: Any?) Compares this object against the specified object.
Int	hashCode() Returns a hash code for this Double object.
static Int	hashCode(value: Double) Returns a hash code for a double value; compatible with Double.hashCode().
static Boolean	isFinite(d: Double) Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).
Boolean	isInfinite() Returns true if this Double value is infinitely large in magnitude, false otherwise.
static Boolean	isInfinite(v: Double) Returns true if the specified number is infinitely large in magnitude, false otherwise.
Boolean	isNaN() Returns true if this Double value is a Not-a-Number (NaN), false otherwise.
static Boolean	isNaN(v: Double) Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
static Double	longBitsToDouble(bits: Long) Returns the double value corresponding to a given bit representation.
static Double	max(a: Double, b: Double) Returns the greater of two double values as if by calling Math.max.
static Double	min(a: Double, b: Double) Returns the smaller of two double values as if by calling Math.min.
static Double	parseDouble(s: String) Returns a new double initialized to the value represented by the specified String, as performed by the valueOf method of class Double.
static Double	sum(a: Double, b: Double) Adds two double values together as per the + operator.
Byte	toByte() Returns the value of this Double as a byte after a narrowing primitive conversion.
Double	toDouble() Returns the double value of this Double object.
Float	toFloat() Returns the value of this Double as a float after a narrowing primitive conversion.
static String	toHexString(d: Double) Returns a hexadecimal string representation of the double argument.
Int	toInt() Returns the value of this Double as an int after a narrowing primitive conversion.
Long	toLong() Returns the value of this Double as a long after a narrowing primitive conversion.
Short	toShort() Returns the value of this Double as a short after a narrowing primitive conversion.
String	toString() Returns a string representation of this Double object.
static String	toString(d: Double) Returns a string representation of the double argument.
static Double	valueOf(d: Double) Returns a Double instance representing the specified double value.
static Double	valueOf(s: String) Returns a object holding the value represented by the argument string .

Properties
static Class<Double!>!	TYPE The Class instance representing the primitive type double.

Constants

BYTES

Added in API level 24

static val BYTES: Int

The number of bytes used to represent a double value.

Value: 8

MAX_EXPONENT

Added in API level 9

static val MAX_EXPONENT: Int

Maximum exponent a finite double variable may have. It is equal to the value returned by Math.getExponent(Double.MAX_VALUE).

Value: 1023

MAX_VALUE

Added in API level 1

static val MAX_VALUE: Double

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).

Value: 1.7976931348623157E308

MIN_EXPONENT

Added in API level 9

static val MIN_EXPONENT: Int

Minimum exponent a normalized double variable may have. It is equal to the value returned by Math.getExponent(Double.MIN_NORMAL).

Value: -1022

MIN_NORMAL

Added in API level 9

static val MIN_NORMAL: Double

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).

Value: 2.2250738585072014E-308

MIN_VALUE

Added in API level 1

static val MIN_VALUE: Double

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).

Value: 4.9E-324

NEGATIVE_INFINITY

Added in API level 1

static val NEGATIVE_INFINITY: Double

A constant holding the negative infinity of type double. It is equal to the value returned by Double.longBitsToDouble(0xfff0000000000000L).

Value: (-1.0/0.0)

NaN

Added in API level 1

static val NaN: Double

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

Value: (0.0/0.0)

POSITIVE_INFINITY

Added in API level 1

static val POSITIVE_INFINITY: Double

A constant holding the positive infinity of type double. It is equal to the value returned by Double.longBitsToDouble(0x7ff0000000000000L).

Value: (1.0/0.0)

PRECISION

Added in API level 35

static val PRECISION: Int

The number of bits in the significand of a double value. This is the parameter N in section {@jls 4.2.3} of The Java Language Specification.

Value: 53

SIZE

Added in API level 1

static val SIZE: Int

The number of bits used to represent a double value.

Value: 64

Public constructors

Double

Added in API level 1

Double(value: Double)

Deprecated: It is rarely appropriate to use this constructor. The static factory valueOf(double) is generally a better choice, as it is likely to yield significantly better space and time performance.

Constructs a newly allocated Double object that represents the primitive double argument.

Parameters
value	Double: the value to be represented by the Double.

Double

Added in API level 1

Double(s: String)

Deprecated: It is rarely appropriate to use this constructor. Use parseDouble(java.lang.String) to convert a string to a double primitive, or use valueOf(java.lang.String) to convert a string to a Double object.

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
s	String: a string to be converted to a Double.

Exceptions
java.lang.NumberFormatException	if the string does not contain a parsable number.

Public methods

compare

Added in API level 1

static fun compare(
    d1: Double, 
    d2: Double
): Int

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
d1	Double: the first double to compare
d2	Double: the second double to compare

Return
Int	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.

compareTo

Added in API level 1

fun compareTo(other: Double): Int

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.

Parameters
o	the object to be compared.
anotherDouble	the Double to be compared.

Return
Int	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.

Exceptions
java.lang.NullPointerException	if the specified object is null
java.lang.ClassCastException	if the specified object's type prevents it from being compared to this object.

doubleToLongBits

Added in API level 1

static fun doubleToLongBits(value: Double): Long

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	Double: a double precision floating-point number.

Return
Long	the bits that represent the floating-point number.

doubleToRawLongBits

Added in API level 1

static fun doubleToRawLongBits(value: Double): Long

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	Double: a double precision floating-point number.

Return
Long	the bits that represent the floating-point number.

equals

Added in API level 1

fun equals(other: Any?): Boolean

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.

Parameters
obj	the reference object with which to compare.

Return
Boolean	true if this object is the same as the obj argument; false otherwise.

See Also

• java.lang.Double#doubleToLongBits(double)

hashCode

Added in API level 1

fun hashCode(): Int

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());

Return
Int	a hash code value for this object.

hashCode

Added in API level 24

static fun hashCode(value: Double): Int

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

Parameters
value	Double: the value to hash

Return
Int	a hash code value for a double value.

isFinite

Added in API level 24

static fun isFinite(d: Double): Boolean

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

Parameters
d	Double: the double value to be tested

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

isInfinite

Added in API level 1

fun isInfinite(): Boolean

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

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

isInfinite

Added in API level 1

static fun isInfinite(v: Double): Boolean

Returns true if the specified number is infinitely large in magnitude, false otherwise.

Parameters
v	Double: the value to be tested.

Return
Boolean	true if the value of the argument is positive infinity or negative infinity; false otherwise.

isNaN

Added in API level 1

fun isNaN(): Boolean

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

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

isNaN

Added in API level 1

static fun isNaN(v: Double): Boolean

Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.

Parameters
v	Double: the value to be tested.

Return
Boolean	true if the value of the argument is NaN; false otherwise.

longBitsToDouble

Added in API level 1

static fun longBitsToDouble(bits: Long): Double

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:

<code>int s = ((bits &gt;&gt; 63) == 0) ? 1 : -1;
  int e = (int)((bits &gt;&gt; 52) &amp; 0x7ffL);
  long m = (e == 0) ?
                  (bits &amp; 0xfffffffffffffL) &lt;&lt; 1 :
                  (bits &amp; 0xfffffffffffffL) | 0x10000000000000L;
  </code>

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
bits	Long: any long integer.

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

max

Added in API level 24

static fun max(
    a: Double, 
    b: Double
): Double

Returns the greater of two double values as if by calling Math.max.

Parameters
a	Double: the first operand
b	Double: the second operand

Return
Double	the greater of a and b

See Also

• java.util.function.BinaryOperator

min

Added in API level 24

static fun min(
    a: Double, 
    b: Double
): Double

Returns the smaller of two double values as if by calling Math.min.

Parameters
a	Double: the first operand
b	Double: the second operand

Return
Double	the smaller of a and b.

See Also

• java.util.function.BinaryOperator

parseDouble

Added in API level 1

static fun parseDouble(s: String): Double

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

Parameters
s	String: the string to be parsed.

Return
Double	the double value represented by the string argument.

Exceptions
java.lang.NullPointerException	if the string is null
java.lang.NumberFormatException	if the string does not contain a parsable double.

See Also

• java.lang.Double#valueOf(String)

sum

Added in API level 24

static fun sum(
    a: Double, 
    b: Double
): Double

Adds two double values together as per the + operator.

Parameters
a	Double: the first operand
b	Double: the second operand

Return
Double	the sum of a and b

See Also

• java.util.function.BinaryOperator

toByte

Added in API level 1

fun toByte(): Byte

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

Return
Byte	the double value represented by this object converted to type byte

toDouble

Added in API level 1

fun toDouble(): Double

Returns the double value of this Double object.

Return
Double	the double value represented by this object

toFloat

Added in API level 1

fun toFloat(): Float

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

Return
Float	the double value represented by this object converted to type float

toHexString

Added in API level 1

static fun toHexString(d: Double): String

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 '-' ('\u005Cu002D'); 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	Double: the double to be converted.

Return
String	a hex string representation of the argument.

toInt

Added in API level 1

fun toInt(): Int

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

Return
Int	the double value represented by this object converted to type int

toLong

Added in API level 1

fun toLong(): Long

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

Return
Long	the double value represented by this object converted to type long

toShort

Added in API level 1

fun toShort(): Short

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

Return
Short	the double value represented by this object converted to type short

toString

Added in API level 1

fun toString(): String

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
String	a String representation of this object.

See Also

• java.lang.Double#toString(double)

toString

Added in API level 1

static fun toString(d: Double): String

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 '-' ('\u005Cu002D'); 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 '.' ('\u005Cu002E'), 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 < 10n+1; then let a be the mathematically exact quotient of m and 10n so that 1 ≤ a < 10. The magnitude is then represented as the integer part of a, as a single decimal digit, followed by '.' ('\u005Cu002E'), followed by decimal digits representing the fractional part of a, followed by the letter 'E' ('\u005Cu0045'), 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
d	Double: the double to be converted.

Return
String	a string representation of the argument.

valueOf

Added in API level 1

static fun valueOf(d: Double): Double

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	Double: a double value.

Return
Double	a Double instance representing d.

valueOf

Added in API level 1

static fun valueOf(s: String): Double

Returns a object holding the value represented by the argument string .

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 java.lang.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, 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 .

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:

<code>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
   }
  </code>

Parameters
s	String: the string to be parsed.

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

Exceptions
java.lang.NumberFormatException	if the string does not contain a parsable number.

Properties

TYPE

Added in API level 1

static val TYPE: Class<Double!>!

The Class instance representing the primitive type double.