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Class OptionalLong

public final class OptionalLong
extends Object

A container object which may or may not contain a long value. If a value is present, isPresent() will return true and getAsLong() 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 OptionalLong may have unpredictable results and should be avoided.

Since:
1.8

Methods

empty

public static OptionalLong empty()

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

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 OptionalLong.

of

public static OptionalLong of(long value)

Return an OptionalLong with the specified value present.

Parameters:
value - the value to be present
Returns:
an OptionalLong with the value present

getAsLong

public long getAsLong()

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

Returns:
the value held by this OptionalLong
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(LongConsumer 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 long orElse(long 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 long orElseGet(LongSupplier other)

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

Parameters:
other - a LongSupplier whose result is returned if no value is present
Returns:
the value if present otherwise the result of other.getAsLong()
Throws:
NullPointerException - if value is not present and other is null

orElseThrow

public <X extends Throwable> long 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 OptionalLong. The other object is considered equal if:

  • it is also an OptionalLong and;
  • both instances have no value present or;
  • the present values are "equal to" each other via ==.
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

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Documentation extracted from Debian's OpenJDK Development Kit package.
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