程序包 java.util

类 OptionalDouble

java.lang.Object

java.util.OptionalDouble

public final class OptionalDouble
extends Object

A container object which may or may not contain a double value. If a value is present, isPresent() will return true and getAsDouble() will return the value.

Additional methods that depend on the presence or absence of a contained value are provided, such as orElse() (return a default value if value not present) and ifPresent() (execute a block of code if the value is present).

This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of OptionalDouble may have unpredictable results and should be avoided.

从以下版本开始:

1.8

方法概要

限定符和类型	方法	说明
static OptionalDouble	empty()	Returns an empty OptionalDouble instance.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this OptionalDouble.
double	getAsDouble()	If a value is present in this OptionalDouble, returns the value, otherwise throws NoSuchElementException.
int	hashCode()	Returns the hash code value of the present value, if any, or 0 (zero) if no value is present.
void	ifPresent(DoubleConsumer consumer)	Have the specified consumer accept the value if a value is present, otherwise do nothing.
boolean	isPresent()	Return true if there is a value present, otherwise false.
static OptionalDouble	of(double value)	Return an OptionalDouble with the specified value present.
double	orElse(double other)	Return the value if present, otherwise return other.
double	orElseGet(DoubleSupplier other)	Return the value if present, otherwise invoke other and return the result of that invocation.
<X extends Throwable> double	orElseThrow(Supplier<X> exceptionSupplier)	Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
String	toString()	Returns a string representation of the object.

从类继承的方法 java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

方法详细资料

empty

public static OptionalDouble empty()

Returns an empty OptionalDouble instance. No value is present for this OptionalDouble.

返回:

an empty OptionalDouble.

of

public static OptionalDouble of(double value)

Return an OptionalDouble with the specified value present.

参数:

value - the value to be present

返回:

an OptionalDouble with the value present

getAsDouble

public double getAsDouble()

If a value is present in this OptionalDouble, returns the value, otherwise throws NoSuchElementException.

返回:

the value held by this OptionalDouble

抛出:

NoSuchElementException - if there is no value present

另请参阅:

isPresent()

isPresent

public boolean isPresent()

Return true if there is a value present, otherwise false.

返回:

true if there is a value present, otherwise false

ifPresent

public void ifPresent(DoubleConsumer consumer)

Have the specified consumer accept the value if a value is present, otherwise do nothing.

参数:

consumer - block to be executed if a value is present

抛出:

NullPointerException - if value is present and consumer is null

orElse

public double orElse(double other)

Return the value if present, otherwise return other.

参数:

other - the value to be returned if there is no value present

返回:

the value, if present, otherwise other

orElseGet

public double orElseGet(DoubleSupplier other)

Return the value if present, otherwise invoke other and return the result of that invocation.

参数:

other - a DoubleSupplier whose result is returned if no value is present

返回:

the value if present otherwise the result of other.getAsDouble()

抛出:

NullPointerException - if value is not present and other is null

orElseThrow

public <X extends Throwable> double orElseThrow(Supplier<X> exceptionSupplier)
                                         throws X extends Throwable

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

类型参数:

X - Type of the exception to be thrown

参数:

exceptionSupplier - The supplier which will return the exception to be thrown

返回:

the present value

抛出:

X - if there is no value present

NullPointerException - if no value is present and exceptionSupplier is null

X extends Throwable

equals

public boolean equals(Object obj)

Indicates whether some other object is "equal to" this OptionalDouble. The other object is considered equal if:

• it is also an OptionalDouble and;
• both instances have no value present or;
• the present values are "equal to" each other via Double.compare() == 0.

覆盖:

equals 在类中 Object

参数:

obj - an object to be tested for equality

返回:

{code true} if the other object is "equal to" this object otherwise false

另请参阅:

Object.hashCode(), HashMap

hashCode

public int hashCode()

Returns the hash code value of the present value, if any, or 0 (zero) if no value is present.

覆盖:

hashCode 在类中 Object

返回:

hash code value of the present value or 0 if no value is present

另请参阅:

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

toString

public String toString()

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Returns a non-empty string representation of this object suitable for debugging. The exact presentation format is unspecified and may vary between implementations and versions.

覆盖:

toString 在类中 Object

返回:

the string representation of this instance