Java compact1, compact2, compact3 java.util Class OptionalDouble（JDK8）

Method Detail

• empty

  public static OptionalDouble empty()

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

  API Note:

  Though it may be tempting to do so, avoid testing if an object is empty by comparing with == against instances returned by Option.empty(). There is no guarantee that it is a singleton. Instead, use isPresent().

  Returns:

  an empty OptionalDouble.

• of

  public static OptionalDouble of(double value)

  Return an OptionalDouble with the specified value present.

  Parameters:

  value - the value to be present

  Returns:

  an OptionalDouble with the value present

• getAsDouble

  public double getAsDouble()

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

  Returns:

  the value held by this OptionalDouble

  Throws:

  NoSuchElementException - if there is no value present

  See Also:

  isPresent()

• isPresent

  public boolean isPresent()

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

  Returns:

  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.

  Parameters:

  consumer - block to be executed if a value is present

  Throws:

  NullPointerException - if value is present and consumer is null

• orElse

  public double orElse(double other)

  Return the value if present, otherwise return other.

  Parameters:

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

  Returns:

  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.

  Parameters:

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

  Returns:

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

  Throws:

  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.

  API Note:

  A method reference to the exception constructor with an empty argument list can be used as the supplier. For example, IllegalStateException::new

  Type Parameters:

  X - Type of the exception to be thrown

  Parameters:

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

  Returns:

  the present value

  Throws:

  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.

  Overrides:

  equals in class Object

  Parameters:

  obj - an object to be tested for equality

  Returns:

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

  See Also:

  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.

  Overrides:

  hashCode in class Object

  Returns:

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

  See Also:

  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.

  Overrides:

  toString in class Object

  Implementation Requirements:

  If a value is present the result must include its string representation in the result. Empty and present instances must be unambiguously differentiable.

  Returns:

  the string representation of this instance