org.apache.spark.api.java

Class Optional<T>

java.lang.Object

org.apache.spark.api.java.Optional<T>

Type Parameters:

T - type of value held inside

All Implemented Interfaces:

java.io.Serializable

public final class Optional<T>
extends java.lang.Object
implements java.io.Serializable

Like java.util.Optional in Java 8, scala.Option in Scala, and com.google.common.base.Optional in Google Guava, this class represents a value of a given type that may or may not exist. It is used in methods that wish to optionally return a value, in preference to returning null.

In fact, the class here is a reimplementation of the essential API of both java.util.Optional and com.google.common.base.Optional. From java.util.Optional, it implements:

• empty()
• of(Object)
• ofNullable(Object)
• get()
• orElse(Object)
• isPresent()

From com.google.common.base.Optional it implements:

• absent()
• of(Object)
• fromNullable(Object)
• get()
• or(Object)
• orNull()
• isPresent()

java.util.Optional itself is not used at this time because the project does not require Java 8. Using com.google.common.base.Optional has in the past caused serious library version conflicts with Guava that can't be resolved by shading. Hence this work-alike clone.

See Also:

Serialized Form

Method Summary

Methods

Modifier and Type	Method and Description
static <T> Optional<T>	absent()
static <T> Optional<T>	empty()
boolean	equals(java.lang.Object obj)
static <T> Optional<T>	fromNullable(T value)
T	get()
int	hashCode()
boolean	isPresent()
static <T> Optional<T>	of(T value)
static <T> Optional<T>	ofNullable(T value)
T	or(T other)
T	orElse(T other)
T	orNull()
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

empty

public static <T> Optional<T> empty()

Returns:

an empty Optional

of

public static <T> Optional<T> of(T value)

Parameters:

value - non-null value to wrap

Returns:

Optional wrapping this value

Throws:

java.lang.NullPointerException - if value is null

ofNullable

public static <T> Optional<T> ofNullable(T value)

Parameters:

value - value to wrap, which may be null

Returns:

Optional wrapping this value, which may be empty

get

public T get()

Returns:

the value wrapped by this Optional

Throws:

java.lang.NullPointerException - if this is empty (contains no value)

orElse

public T orElse(T other)

Parameters:

other - value to return if this is empty

Returns:

this Optional's value if present, or else the given value

isPresent

public boolean isPresent()

Returns:

true iff this Optional contains a value (non-empty)

absent

public static <T> Optional<T> absent()

Returns:

an empty Optional

fromNullable

public static <T> Optional<T> fromNullable(T value)

Parameters:

value - value to wrap, which may be null

Returns:

Optional wrapping this value, which may be empty

or

public T or(T other)

Parameters:

other - value to return if this is empty

Returns:

this Optional's value if present, or else the given value

orNull

public T orNull()

Returns:

this Optional's value if present, or else null

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object