OpenJDK 27 · java.lang.Double · APIdia, the JavaDoc alternative

The Double class is the wrapper class for values of the primitive type double. 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.

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

Floating-point Equality, Equivalence, and Comparison

IEEE 754 floating-point values include finite nonzero values, signed zeros (+0.0 and -0.0), signed infinities (positive infinity 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 uses representation equivalence, defining NaN arguments to be equal to each other, restoring reflexivity, and defining +0.0 to not be equal to -0.0. For comparisons, compareTo defines a total order where -0.0 is less than +0.0 and where a NaN is equal to itself and considered greater than positive infinity.

The operational semantics 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.

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

numerical equality (== operator): (Not an equivalence relation)

Two floating-point values represent the same extended real number. The extended real numbers are the real numbers augmented with positive infinity and negative infinity. Under numerical equality, +0.0 and -0.0 are equal since they both map to the same real value, 0. A NaN does not map to any real number and is not equal to any value, including itself.

bit-wise equivalence:

The bits of the two floating-point values are the same. This equivalence relation for double values a and b is implemented by the expression
Double.doubleToRawLongBits(a) == Double.doubleToRawLongBits(b)
Under this relation, +0.0 and -0.0 are distinguished from each other and every bit pattern encoding a NaN is distinguished from every other bit pattern encoding a NaN.

representation equivalence:

The two floating-point values represent the same IEEE 754 datum. In particular, for finite values, the sign, exponent, and significand components of the floating-point values are the same. Under this relation:

+0.0 and -0.0 are distinguished from each other.
every bit pattern encoding a NaN is considered equivalent to each other
positive infinity is equivalent to positive infinity; negative infinity is equivalent to negative infinity.

Expressions implementing this equivalence relation include:

Double.doubleToLongBits(a) == Double.doubleToLongBits(b)
Double.valueOf(a).equals(Double.valueOf(b))
Double.compare(a, b) == 0

Note that representation equivalence is often an appropriate notion of equivalence to test the behavior of math libraries.

For two binary floating-point values a and b, if neither of a and b is zero or NaN, then the three relations numerical equality, bit-wise equivalence, and representation equivalence of a and b have the same true/false value. In other words, for binary floating-point values, the three relations only differ if at least one argument is zero or NaN.

Decimal ↔ Binary Conversion Issues

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

Values of the float type have 24 bits of precision and values of the double type have 53 bits of precision. Therefore, since 0.1 is a repeating fraction in base 2 with a four-bit repeat, 0.1f != 0.1d. In more detail, including hexadecimal floating-point literals:

The exact numerical value of 0.1f (0x1.99999a0000000p-4f) is 0.100000001490116119384765625.
The exact numerical value of 0.1d (0x1.999999999999ap-4d) is 0.1000000000000000055511151231257827021181583404541015625.

These are the closest float and double values, respectively, to the numerical value of 0.1. These results are consistent with a float value having the equivalent of 6 to 9 digits of decimal precision and a double value having the equivalent of 15 to 17 digits of decimal precision. (The equivalent precision varies according to the different relative densities of binary and decimal values at different points along the real number line.)

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

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

For each finite floating-point value and a given floating-point type, there is a contiguous region of the real number line which maps to that value. Under the default round to nearest rounding policy (JLS 15.4), this contiguous region for a value is typically one ulp (unit in the last place) wide and centered around the exactly representable value. (At exponent boundaries, the region is asymmetrical and larger on the side with the larger exponent.) For example, for 0.1f, the region can be computed as follows:
// Numeric values listed are exact values
oneTenthApproxAsFloat = 0.100000001490116119384765625;
ulpOfoneTenthApproxAsFloat = Math.ulp(0.1f) = 7.450580596923828125E-9;
// Numeric range that is converted to the float closest to 0.1, _excludes_ endpoints
(oneTenthApproxAsFloat - ½ulpOfoneTenthApproxAsFloat, oneTenthApproxAsFloat + ½ulpOfoneTenthApproxAsFloat) =
(0.0999999977648258209228515625, 0.1000000052154064178466796875)

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

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

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

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

greater than the exact result
equal to the exact result
less than the exact result

A floating-point value doesn't "know" whether it was the result of rounding up, or rounding down, or an exact operation; it contains no history of how it was computed. Consequently, the sum of

0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f + 0.1f;
// Numerical value of computed sum: 1.00000011920928955078125,
// the next floating-point value larger than 1.0f, equal to Math.nextUp(1.0f).

0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d + 0.1d;
// Numerical value of computed sum: 0.99999999999999988897769753748434595763683319091796875,
// the next floating-point value smaller than 1.0d, equal to Math.nextDown(1.0d).

should not be expected to be exactly equal to 1.0, but only to be close to 1.0. Consequently, the following code is an infinite loop:

double d = 0.0;
while (d != 1.0) { // Surprising infinite loop
  d += 0.1; // Sum never _exactly_ equals 1.0
}

Instead, use an integer loop count for counted loops:

double d = 0.0;
for (int i = 0; i < 10; i++) {
  d += 0.1;
} // Value of d is equal to Math.nextDown(1.0).

or test against a floating-point limit using ordered comparisons (<, <=, >, >=):

double d = 0.0;
while (d <= 1.0) {
  d += 0.1;
} // Value of d approximately 1.0999999999999999

While floating-point arithmetic may have surprising results, IEEE 754 floating-point arithmetic follows a principled design and its behavior is predictable on the Java platform.

Field Summary

Modifier and Type	Field and Description
public static final int	BYTES The number of bytes used to represent a `double` value, .
public static final int	MAX_EXPONENT Maximum exponent a finite `double` variable may have, .
public static final double	MAX_VALUE A constant holding the largest positive finite value of type `double`, (2-2^-52)·2¹⁰²³.
public static final int	MIN_EXPONENT Minimum exponent a normalized `double` variable may have, .
public static final double	MIN_NORMAL A constant holding the smallest positive normal value of type `double`, 2^-1022.
public static final double	MIN_VALUE A constant holding the smallest positive nonzero value of type `double`, 2^-1074.
public static final double	NaN A constant holding a Not-a-Number (NaN) value of type `double`.
public static final double	NEGATIVE_INFINITY A constant holding the negative infinity of type `double`.
public static final double	POSITIVE_INFINITY A constant holding the positive infinity of type `double`.
public static final int	PRECISION The number of bits in the significand of a `double` value, .
private static final long	serialVersionUID Hides java.lang.Number.serialVersionUID. use serialVersionUID from JDK 1.0.2 for interoperability
public static final int	SIZE The number of bits used to represent a `double` value, .
public static final Class<Double>	TYPE The `Class` instance representing the primitive type `double`.
private final double	value The value of the Double.

Constructor Summary

Access	Constructor and Description
public	Double(double the value to be represented by the `Double`. value) Deprecated since 9. It is rarely appropriate to use this constructor. Constructs a newly allocated `Double` object that represents the primitive `double` argument.
public	Double(String a string to be converted to a `Double`. s) Deprecated since 9. It is rarely appropriate to use this constructor. Constructs a newly allocated `Double` object that represents the floating-point value of type `double` represented by the string.

Method Summary

Modifier and Type	Method and Description
public byte	Returns: the `double` value represented by this object converted to type `byte` byteValue() Overrides java.lang.Number.byteValue. Returns the value of this `Double` as a `byte` after a narrowing primitive conversion.
public static int	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`. compare(double the first `double` to compare d1, double the second `double` to compare d2) Compares the two specified `double` values.
public int	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`. compareTo(Double the `Double` to be compared. anotherDouble) Implements java.lang.Comparable.compareTo. Compares two `Double` objects numerically.
public Optional<Double>	Returns: an `Optional` describing the Double instance describeConstable() Implements java.lang.constant.Constable.describeConstable. Returns an `Optional` containing the nominal descriptor for this instance, which is the instance itself.
public static long	Returns: the bits that represent the floating-point number. doubleToLongBits(double a `double` precision floating-point number. value) Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout.
public static native long	Returns: the bits that represent the floating-point number. doubleToRawLongBits(double a `double` precision floating-point number. 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.
public double	Returns: the `double` value represented by this object doubleValue() Implements abstract java.lang.Number.doubleValue. Returns the `double` value of this `Double` object.
public boolean	equals(Object obj) Overrides java.lang.Object.equals. Compares this object against the specified object.
public float	Returns: the `double` value represented by this object converted to type `float` floatValue() Implements abstract java.lang.Number.floatValue. Returns the value of this `Double` as a `float` after a narrowing primitive conversion.
public int	Returns: a `hash code` value for this object. hashCode() Overrides java.lang.Object.hashCode. Returns a hash code for this `Double` object.
public static int	Returns: a hash code value for a `double` value. hashCode(double the value to hash value) Returns a hash code for a `double` value; compatible with `Double.hashCode()`.
public int	Returns: the `double` value represented by this object converted to type `int` intValue() Implements abstract java.lang.Number.intValue. Returns the value of this `Double` as an `int` after a narrowing primitive conversion.
public static boolean	Returns: `true` if the argument is a finite floating-point value, `false` otherwise. isFinite(double the `double` value to be tested d) Returns `true` if the argument is a finite floating-point value; returns `false` otherwise (for NaN and infinity arguments).
public static boolean	Returns: `true` if the value of the argument is positive infinity or negative infinity; `false` otherwise. isInfinite(double the value to be tested. v) Returns `true` if the specified number is infinitely large in magnitude, `false` otherwise.
public boolean	Returns: `true` if the value represented by this object is positive infinity or negative infinity; `false` otherwise. isInfinite() Returns `true` if this `Double` value is infinitely large in magnitude, `false` otherwise.
public static boolean	Returns: `true` if the value of the argument is NaN; `false` otherwise. isNaN(double the value to be tested. v) Returns `true` if the specified number is a Not-a-Number (NaN) value, `false` otherwise.
public boolean	Returns: `true` if the value represented by this object is NaN; `false` otherwise. isNaN() Returns `true` if this `Double` value is a Not-a-Number (NaN), `false` otherwise.
public static native double	Returns: the `double` floating-point value with the same bit pattern. longBitsToDouble(long any `long` integer. bits) Returns the `double` value corresponding to a given bit representation.
public long	Returns: the `double` value represented by this object converted to type `long` longValue() Implements abstract java.lang.Number.longValue. Returns the value of this `Double` as a `long` after a narrowing primitive conversion.
public static double	Returns: the greater of `a` and `b` max(double the first operand a, double the second operand b) Returns the greater of two `double` values as if by calling `Math.max`.
public static double	Returns: the smaller of `a` and `b`. min(double the first operand a, double the second operand b) Returns the smaller of two `double` values as if by calling `Math.min`.
public static double	Returns: the `double` value represented by the string argument. parseDouble(String the string to be parsed. s) Returns a new `double` initialized to the value represented by the specified `String`, as performed by the `valueOf` method of class `Double`.
public Double	Returns: the Double instance resolveConstantDesc(MethodHandles.Lookup ignored lookup) Implements java.lang.constant.ConstantDesc.resolveConstantDesc. Resolves this instance as a `ConstantDesc`, the result of which is the instance itself.
public short	Returns: the `double` value represented by this object converted to type `short` shortValue() Overrides java.lang.Number.shortValue. Returns the value of this `Double` as a `short` after a narrowing primitive conversion.
public static double	Returns: the sum of `a` and `b` sum(double the first operand a, double the second operand b) Adds two `double` values together as per the + operator.
public static String	Returns: a hex string representation of the argument. toHexString(double the `double` to be converted. d) Returns a hexadecimal string representation of the `double` argument.
public static String	Returns: a string representation of the argument. toString(double the `double` to be converted. d) Returns a string representation of the `double` argument.
public String	Returns: a `String` representation of this object. toString() Overrides java.lang.Object.toString. Returns a string representation of this `Double` object.
public static Double	Returns: a `Double` object holding the value represented by the `String` argument. valueOf(String the string to be parsed. s) Returns a `Double` object holding the `double` value represented by the argument string `s`.
public static Double	Returns: a `Double` instance representing `d`. valueOf(double a double value. d) Returns a `Double` instance representing the specified `double` value.

Field Detail

BYTES back to summary

BYTES	back to summary
public static final int BYTES The number of bytes used to represent a `double` value, . Since 1.8

public static final int BYTES

The number of bytes used to represent a double value, .

Since: 1.8

MAX_EXPONENT back to summary

MAX_EXPONENT	back to summary
public static final int MAX_EXPONENT Maximum exponent a finite `double` variable may have, . It is equal to the value returned by `Math.getExponent(Double.MAX_VALUE)`. Since 1.6

public static final int MAX_EXPONENT

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

Since: 1.6

MAX_VALUE	back to summary
public static final double MAX_VALUE 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 back to summary

MIN_EXPONENT	back to summary
public static final int MIN_EXPONENT Minimum exponent a normalized `double` variable may have, . It is equal to the value returned by `Math.getExponent(Double.MIN_NORMAL)`. Since 1.6

public static final int MIN_EXPONENT

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

Since: 1.6

MIN_NORMAL back to summary

MIN_NORMAL	back to summary
public static final double MIN_NORMAL 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)`. Since 1.6

public static final double MIN_NORMAL

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).

Since: 1.6

MIN_VALUE	back to summary
public static final double MIN_VALUE 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)`.

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

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

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

PRECISION back to summary

PRECISION	back to summary
public static final int PRECISION The number of bits in the significand of a `double` value, . This is the parameter N in section 4.2.3 of The Java Language Specification. Since 19

public static final int PRECISION

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

Since: 19

serialVersionUID	back to summary
private static final long serialVersionUID Hides java.lang.Number.serialVersionUID. use serialVersionUID from JDK 1.0.2 for interoperability Annotations @Serial

serialVersionUID

back to summary

private static final long serialVersionUID

Hides java.lang.Number.serialVersionUID.

use serialVersionUID from JDK 1.0.2 for interoperability

Annotations

@Serial

SIZE back to summary

SIZE	back to summary
public static final int SIZE The number of bits used to represent a `double` value, . Since 1.5

public static final int SIZE

The number of bits used to represent a double value, .

Since: 1.5

TYPE back to summary

TYPE	back to summary
public static final Class<Double> TYPE The `Class` instance representing the primitive type `double`. Since 1.1

public static final Class<Double> TYPE

The Class instance representing the primitive type double.

Since: 1.1

value	back to summary
private final double value The value of the Double.

Constructor Detail

Double back to summary

Double	back to summary
public Double(double value) Deprecated since 9. 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`. Annotations @Deprecated since:9

public Double(double value)

Deprecated

since 9.

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.

Annotations

@Deprecated
since:9

Double back to summary

Double	back to summary
public Double(String s) throws NumberFormatException Deprecated since 9. It is rarely appropriate to use this constructor. Use `parseDouble(String)` to convert a string to a `double` primitive, or use `valueOf(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`. Annotations @Deprecated since:9 Exceptions NumberFormatException: if the string does not contain a parsable number.

public Double(String s) throws NumberFormatException

Deprecated

since 9.

It is rarely appropriate to use this constructor. Use parseDouble(String) to convert a string to a double primitive, or use valueOf(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.

Annotations

@Deprecated
since:9

Exceptions

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

Method Detail

byteValue back to summary

byteValue	back to summary
public byte byteValue() Overrides java.lang.Number.byteValue. Returns the value of this `Double` as a `byte` after a narrowing primitive conversion. Returns:byte the `double` value represented by this object converted to type `byte` Annotations @Override Since 1.1 Java Language Specification 5.1.3 Narrowing Primitive Conversion

public byte byteValue()

Overrides java.lang.Number.byteValue.

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

Returns:byte

the double value represented by this object converted to type byte

Annotations

@Override

Since

1.1

Java Language Specification

5.1.3 Narrowing Primitive Conversion

compare back to summary

compare	back to summary
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)) API Note One idiom to implement representation equivalence on `double` values is `Double.compare(a, b) == 0` Double.compare(a, b) == 0 Parameters d1:double the first `double` to compare d2:double the second `double` to compare Returns: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`. Since 1.4

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))

API Note

One idiom to implement representation equivalence on double values is

Double.compare(a, b) == 0

Parameters

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

Returns: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.

Since

1.4

compareTo back to summary

compareTo	back to summary
public int compareTo(Double anotherDouble) Implements java.lang.Comparable.compareTo. 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. API Note The inclusion of a total order idiom in the Java SE API predates the inclusion of that functionality in the IEEE 754 standard. The ordering of the totalOrder predicate chosen by IEEE 754 differs from the total order chosen by this method. While this method treats all NaN representations as being in the same equivalence class, the IEEE 754 total order defines an ordering based on the bit patterns of the NaN among the different NaN representations. The IEEE 754 order regards "negative" NaN representations, that is NaN representations whose sign bit is set, to be less than any finite or infinite value and less than any "positive" NaN. In addition, the IEEE order regards all positive NaN values as greater than positive infinity. See the IEEE 754 standard for full details of its total ordering. Parameters anotherDouble:Double the `Double` to be compared. Returns: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`. Annotations @Override Since 1.2 Java Language Specification 15.20.1 Numerical Comparison Operators `<`, `<=`, `>`, and `>=`

public int compareTo(Double anotherDouble)

Implements java.lang.Comparable.compareTo.

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.

API Note

The inclusion of a total order idiom in the Java SE API predates the inclusion of that functionality in the IEEE 754 standard. The ordering of the totalOrder predicate chosen by IEEE 754 differs from the total order chosen by this method. While this method treats all NaN representations as being in the same equivalence class, the IEEE 754 total order defines an ordering based on the bit patterns of the NaN among the different NaN representations. The IEEE 754 order regards "negative" NaN representations, that is NaN representations whose sign bit is set, to be less than any finite or infinite value and less than any "positive" NaN. In addition, the IEEE order regards all positive NaN values as greater than positive infinity. See the IEEE 754 standard for full details of its total ordering.

Parameters

anotherDouble:Double: the Double to be compared.

Returns: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.

Annotations

@Override

Since

1.2

Java Language Specification

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

describeConstable back to summary

describeConstable	back to summary
public Optional<Double> describeConstable() Implements java.lang.constant.Constable.describeConstable. Returns an `Optional` containing the nominal descriptor for this instance, which is the instance itself. Returns:Optional<Double> an `Optional` describing the Double instance Annotations @Override Since 12

public Optional<Double> describeConstable()

Implements java.lang.constant.Constable.describeConstable.

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

Returns:Optional<Double>

an Optional describing the Double instance

Annotations

@Override

Since

doubleToLongBits back to summary

doubleToLongBits	back to summary
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:double a `double` precision floating-point number. Returns:long the bits that represent the floating-point number. Annotations @IntrinsicCandidate

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:double: a double precision floating-point number.

Returns:long

the bits that represent the floating-point number.

Annotations

@IntrinsicCandidate

doubleToRawLongBits back to summary

doubleToRawLongBits	back to summary
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 `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. Returns:long the bits that represent the floating-point number. Annotations @IntrinsicCandidate Since 1.3

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.

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.

Returns:long

the bits that represent the floating-point number.

Annotations

@IntrinsicCandidate

Since

1.3

doubleValue back to summary

doubleValue	back to summary
public double doubleValue() Implements abstract java.lang.Number.doubleValue. Returns the `double` value of this `Double` object. Returns:double the `double` value represented by this object Annotations @Override @IntrinsicCandidate

public double doubleValue()

Implements abstract java.lang.Number.doubleValue.

Returns the double value of this Double object.

Returns:double

the double value represented by this object

Annotations

@Override
@IntrinsicCandidate

equals back to summary

equals	back to summary
public boolean equals(Object obj) Overrides java.lang.Object.equals. 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. In other words, representation equivalence is used to compare the `double` values. 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. Java Language Specification 15.21.1 Numerical Equality Operators == and != See Also `java.lang.Double#doubleToLongBits(double)`

public boolean equals(Object obj)

Overrides java.lang.Object.equals.

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. In other words, representation equivalence is used to compare the double values.

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.

Java Language Specification: 15.21.1 Numerical Equality Operators == and !=
See Also: java.lang.Double#doubleToLongBits(double)

floatValue back to summary

floatValue	back to summary
public float floatValue() Implements abstract java.lang.Number.floatValue. Returns the value of this `Double` as a `float` after a narrowing primitive conversion. API Note This method corresponds to the convertFormat operation defined in IEEE 754. Returns:float the `double` value represented by this object converted to type `float` Annotations @Override Since 1.0 Java Language Specification 5.1.3 Narrowing Primitive Conversion

public float floatValue()

Implements abstract java.lang.Number.floatValue.

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

API Note

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

Returns:float

the double value represented by this object converted to type float

Annotations

@Override

Since

1.0

Java Language Specification

5.1.3 Narrowing Primitive Conversion

hashCode back to summary

hashCode	back to summary
public int hashCode() Overrides java.lang.Object.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());` Returns:int a `hash code` value for this object. Annotations @Override

public int hashCode()

Overrides java.lang.Object.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());

Returns:int

a hash code value for this object.

Annotations

@Override

hashCode back to summary

hashCode	back to summary
public static int hashCode(double value) Returns a hash code for a `double` value; compatible with `Double.hashCode()`. Parameters value:double the value to hash Returns:int a hash code value for a `double` value. Since 1.8

public static int hashCode(double value)

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

Parameters

value:double: the value to hash

Returns:int

a hash code value for a double value.

Since

1.8

intValue back to summary

intValue	back to summary
public int intValue() Implements abstract java.lang.Number.intValue. Returns the value of this `Double` as an `int` after a narrowing primitive conversion. API Note This method corresponds to the convertToIntegerTowardZero operation defined in IEEE 754. Returns:int the `double` value represented by this object converted to type `int` Annotations @Override Java Language Specification 5.1.3 Narrowing Primitive Conversion

public int intValue()

Implements abstract java.lang.Number.intValue.

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

API Note

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

Returns:int

the double value represented by this object converted to type int

Annotations

@Override

Java Language Specification

5.1.3 Narrowing Primitive Conversion

isFinite back to summary

isFinite	back to summary
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:double the `double` value to be tested Returns:boolean `true` if the argument is a finite floating-point value, `false` otherwise. Annotations @IntrinsicCandidate Since 1.8

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:double: the double value to be tested

Returns:boolean

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

Annotations

@IntrinsicCandidate

Since

1.8

isInfinite back to summary

isInfinite	back to summary
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:double the value to be tested. Returns:boolean `true` if the value of the argument is positive infinity or negative infinity; `false` otherwise. Annotations @IntrinsicCandidate

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:double: the value to be tested.

Returns:boolean

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

Annotations

@IntrinsicCandidate

isInfinite back to summary

isInfinite	back to summary
public boolean isInfinite() Returns `true` if this `Double` value is infinitely large in magnitude, `false` otherwise. Returns:boolean `true` if the value represented by this object is positive infinity or negative infinity; `false` otherwise.

public boolean isInfinite()

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

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

isNaN back to summary

isNaN	back to summary
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:double the value to be tested. Returns:boolean `true` if the value of the argument is NaN; `false` otherwise.

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:double: the value to be tested.

Returns:boolean

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

isNaN back to summary

isNaN	back to summary
public boolean isNaN() Returns `true` if this `Double` value is a Not-a-Number (NaN), `false` otherwise. Returns:boolean `true` if the value represented by this object is NaN; `false` otherwise.

public boolean isNaN()

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

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

longBitsToDouble back to summary

longBitsToDouble	back to summary
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;` 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:long any `long` integer. Returns:double the `double` floating-point value with the same bit pattern. Annotations @IntrinsicCandidate

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·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:long: any long integer.

Returns:double

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

Annotations

@IntrinsicCandidate

longValue back to summary

longValue	back to summary
public long longValue() Implements abstract java.lang.Number.longValue. Returns the value of this `Double` as a `long` after a narrowing primitive conversion. API Note This method corresponds to the convertToIntegerTowardZero operation defined in IEEE 754. Returns:long the `double` value represented by this object converted to type `long` Annotations @Override Java Language Specification 5.1.3 Narrowing Primitive Conversion

public long longValue()

Implements abstract java.lang.Number.longValue.

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

API Note

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

Returns:long

the double value represented by this object converted to type long

Annotations

@Override

Java Language Specification

5.1.3 Narrowing Primitive Conversion

max back to summary

max	back to summary
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:double the first operand b:double the second operand Returns:double the greater of `a` and `b` Since 1.8 See Also `java.util.function.BinaryOperator`

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:double: the first operand
b:double: the second operand

Returns:double

the greater of a and b

Since

1.8

See Also

java.util.function.BinaryOperator

min back to summary

min	back to summary
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:double the first operand b:double the second operand Returns:double the smaller of `a` and `b`. Since 1.8 See Also `java.util.function.BinaryOperator`

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:double: the first operand
b:double: the second operand

Returns:double

the smaller of a and b.

Since

1.8

See Also

java.util.function.BinaryOperator

parseDouble back to summary

parseDouble	back to summary
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:String the string to be parsed. Returns:double the `double` value represented by the string argument. Exceptions NumberFormatException: if the string does not contain a parsable `double`. NullPointerException: if the string is null Since 1.2 See Also `java.lang.Double#valueOf(String)`, `Decimal ↔ Binary Conversion Issues`

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:String: the string to be parsed.

Returns:double

the double value represented by the string argument.

Exceptions

NumberFormatException:: if the string does not contain a parsable double.
NullPointerException:: if the string is null

Since

1.2

resolveConstantDesc back to summary

resolveConstantDesc	back to summary
public Double resolveConstantDesc(MethodHandles.Lookup lookup) Implements java.lang.constant.ConstantDesc.resolveConstantDesc. Resolves this instance as a `ConstantDesc`, the result of which is the instance itself. Parameters lookup:MethodHandles.Lookup ignored Returns:Double the Double instance Annotations @Override Since 12

public Double resolveConstantDesc(MethodHandles.Lookup lookup)

Implements java.lang.constant.ConstantDesc.resolveConstantDesc.

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

Parameters

lookup:MethodHandles.Lookup: ignored

Returns:Double

the Double instance

Annotations

@Override

Since

shortValue back to summary

shortValue	back to summary
public short shortValue() Overrides java.lang.Number.shortValue. Returns the value of this `Double` as a `short` after a narrowing primitive conversion. Returns:short the `double` value represented by this object converted to type `short` Annotations @Override Since 1.1 Java Language Specification 5.1.3 Narrowing Primitive Conversion

public short shortValue()

Overrides java.lang.Number.shortValue.

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

Returns:short

the double value represented by this object converted to type short

Annotations

@Override

Since

1.1

Java Language Specification

5.1.3 Narrowing Primitive Conversion

sum back to summary

sum	back to summary
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:double the first operand b:double the second operand Returns:double the sum of `a` and `b` Since 1.8 Java Language Specification 4.2.4 Floating-Point Operations See Also `java.util.function.BinaryOperator`

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:double: the first operand
b:double: the second operand

Returns:double

the sum of a and b

Since

1.8

Java Language Specification

4.2.4 Floating-Point Operations

See Also

java.util.function.BinaryOperator

toHexString back to summary

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`

API Note

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

Parameters

d:double: the double to be converted.

Returns:String

a hex string representation of the argument.

Since

1.5

toString back to summary

toString	back to summary
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`…`0`s₁…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_n`0`…`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`.0E`e. For example, 1 × 10²³ is formatted as `1.0E23`. Subcase n > 1: d_m is formatted as s₁`.`s₂…s_n`E`e. For example, 123 × 10^-21 is formatted as `1.23E-19`. To create localized string representations of a floating-point value, use subclasses of `java.text.NumberFormat`. API Note This method corresponds to the general functionality of the convertToDecimalCharacter operation defined in IEEE 754; however, that operation is defined in terms of specifying the number of significand digits used in the conversion. Code to do such a conversion in the Java platform includes converting the `double` to a `BigDecimal` exactly and then rounding the `BigDecimal` to the desired number of digits; sample code: `double d = 0.1; int digits = 25; BigDecimal bd = new BigDecimal(d); String result = bd.round(new MathContext(digits, RoundingMode.HALF_UP)); // 0.1000000000000000055511151` double d = 0.1; int digits = 25; BigDecimal bd = new BigDecimal(d); String result = bd.round(new MathContext(digits, RoundingMode.HALF_UP)); // 0.1000000000000000055511151 Parameters d:double the `double` to be converted. Returns:String a string representation of the argument.

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 java.text.NumberFormat.

API Note

This method corresponds to the general functionality of the convertToDecimalCharacter operation defined in IEEE 754; however, that operation is defined in terms of specifying the number of significand digits used in the conversion. Code to do such a conversion in the Java platform includes converting the double to a BigDecimal exactly and then rounding the BigDecimal to the desired number of digits; sample code:

double d = 0.1;
int digits = 25;
BigDecimal bd = new BigDecimal(d);
String result = bd.round(new MathContext(digits,  RoundingMode.HALF_UP));
// 0.1000000000000000055511151

Parameters

d:double: the double to be converted.

Returns:String

a string representation of the argument.

toString back to summary

toString	back to summary
public String toString() Overrides java.lang.Object.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. Returns:String a `String` representation of this object. See Also `java.lang.Double#toString(double)`

public String toString()

Overrides java.lang.Object.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.

Returns:String: a String representation of this object.
See Also: java.lang.Double#toString(double)

valueOf back to summary

valueOf	back to summary
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. 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 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 } final String Digits = "(\\p{Digit}+)"; final String HexDigits = "(\\p{XDigit}+)"; // an exponent is 'e' or 'E' followed by an optionally // signed decimal integer. final String Exp = "[eE][+-]?"+Digits; final String fpRegex = ("[\\x00-\\x20]"+ // Optional leading "whitespace" "[+-]?(" + // Optional sign character "NaN\|" + // "NaN" string "Infinity\|" + // "Infinity" string // A decimal floating-point string representing a finite positive // number without a leading sign has at most five basic pieces: // Digits . Digits ExponentPart FloatTypeSuffix // // Since this method allows integer-only strings as input // in addition to strings of floating-point literals, the // two sub-patterns below are simplifications of the grammar // productions from section 3.10.2 of // The Java Language Specification. // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)\|"+ // . Digits ExponentPart_opt FloatTypeSuffix_opt "(\\.("+Digits+")("+Exp+")?)\|"+ // Hexadecimal strings "((" + // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt "(0[xX]" + HexDigits + "(\\.)?)\|" + // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" + ")[pP][+-]?" + Digits + "))" + "[fFdD]?))" + "[\\x00-\\x20]");// Optional trailing "whitespace" if (Pattern.matches(fpRegex, myString)) Double.valueOf(myString); // Will not throw NumberFormatException else { // Perform suitable alternative action } API Note To interpret localized string representations of a floating-point value, or string representations that have non-ASCII digits, use `java.text.NumberFormat`. For example, `NumberFormat.getInstance(l).parse(s).doubleValue();` NumberFormat.getInstance(l).parse(s).doubleValue(); where `l` is the desired locale, or `java.util.Locale#ROOT` if locale insensitive. API Note This method corresponds to the convertFromDecimalCharacter and convertFromHexCharacter operations defined in IEEE 754. Parameters s:String the string to be parsed. Returns:Double a `Double` object holding the value represented by the `String` argument. Exceptions NumberFormatException: if the string does not contain a parsable number. See Also `Decimal ↔ Binary Conversion Issues`

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.

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 section 3.10.2 of
      // The Java Language Specification.

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

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

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

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

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

 if (Pattern.matches(fpRegex, myString))
     Double.valueOf(myString); // Will not throw NumberFormatException

 else {
     // Perform suitable alternative action
 }

API Note

To interpret localized string representations of a floating-point value, or string representations that have non-ASCII digits, use java.text.NumberFormat. For example,

NumberFormat.getInstance(l).parse(s).doubleValue();

where l is the desired locale, or java.util.Locale#ROOT if locale insensitive.

API Note

This method corresponds to the convertFromDecimalCharacter and convertFromHexCharacter operations defined in IEEE 754.

Parameters

s:String: the string to be parsed.

Returns:Double

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

Exceptions

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

See Also

Decimal ↔ Binary Conversion Issues

valueOf back to summary

valueOf	back to summary
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:double a double value. Returns:Double a `Double` instance representing `d`. Annotations @IntrinsicCandidate Since 1.5

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:double: a double value.

Returns:Double

a Double instance representing d.

Annotations

@IntrinsicCandidate

Since

1.5

public final Class Double

Floating-point Equality, Equivalence, and Comparison

Decimal ↔ Binary Conversion Issues

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail