Package org.n52.shetland.w3c

Class Nillable<T>

java.lang.Object

org.n52.shetland.w3c.Nillable<T>

Type Parameters:

T - the instance type

public abstract class Nillable<T>
extends Object

Represents a tri-state object: can be nil (with an optional message), absent (or null) or present. isNil(), isAbsent() and isPresent() are mutually exclusive true.

Method Summary

Modifier and Type	Method	Description
static <T> Nillable<T>	absent()	Creates a Nillable for a absent instance.
abstract T	get()	Returns the object if present.
abstract Optional<String>	getNilReason()	Returns the optional reason for this object being nil.
boolean	hasReason()	Checks if this Nillable is nil and has a reason.
static <T> Nillable<T>	inapplicable()	Creates a new Nillable, that is nil because it is inapplicable.
abstract boolean	isAbsent()	Checks if this Nillable is null.
abstract boolean	isNil()	Checks if this Nillable is nil.
boolean	isNull()	Checks if this Nillable is null.
abstract boolean	isPresent()	Checks if this Nillable is present.
boolean	isPresentOrNil()	Checks if this this instance is not absent.
abstract <X> Nillable<X>	map(Function<? super T,X> fun)	Transforms this Nillable to the target type.
static <T> Nillable<T>	missing()	Creates a new Nillable, that is nil because it is missing.
static <T> Nillable<T>	nil()	Creates a new Nillable that is nil.
static <T> Nillable<T>	nil(String reason)	Creates a new Nillable that is nil because of optionally supplied reason.
static <T> Nillable<T>	of(T obj)	Creates a new Nillable that is either present (if obj is not null), or absent.
static <T> Nillable<T>	of(T obj, String reason)	Creates a new Nillable that is either present (if obj is not null), nil (if reason is not null) or absent.
static <T> Nillable<T>	present(T t)	Creates a new Nillable from a present instance.
static <T> Nillable<T>	template()	Creates a new Nillable, that is nil because it is a template value.
static <T> Nillable<T>	unknown()	Creates a new Nillable, that is nil because it is unknown.
static <T> Nillable<T>	withheld()	Creates a new Nillable, that is nil because it is withheld.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

isNil

public abstract boolean isNil()

Checks if this Nillable is nil.

Returns:

whether or not this instance is nil

See Also:

isPresent(), isAbsent()

isPresent

public abstract boolean isPresent()

Checks if this Nillable is present.

Returns:

whether or not this instance is present

See Also:

isNil(), isAbsent()

isAbsent

public abstract boolean isAbsent()

Checks if this Nillable is null.

Returns:

whether or not this instance is null

See Also:

isNil(), isPresent()

map

public abstract <X> Nillable<X> map(Function<? super T,X> fun)

Transforms this Nillable to the target type.

Type Parameters:

X - the target type

Parameters:

fun - the transformation function

Returns:

the Nillable

isNull

public boolean isNull()

Checks if this Nillable is null.

Returns:

whether or not this instance is null

See Also:

isAbsent()

isPresentOrNil

public boolean isPresentOrNil()

Checks if this this instance is not absent.

Returns:

whether this instance is present or nil

get

public abstract T get()

Returns the object if present.

Returns:

the object

Throws:

UnsupportedOperationException - if this instance is not present

See Also:

isPresent()

hasReason

public boolean hasReason()

Checks if this Nillable is nil and has a reason.

Returns:

whether this instance has a nil reason or not

getNilReason

public abstract Optional<String> getNilReason()

Returns the optional reason for this object being nil.

Returns:

the nil reason

Throws:

UnsupportedOperationException - if this instance is not nil

See Also:

isNil()

present

public static <T> Nillable<T> present(T t)

Creates a new Nillable from a present instance.

Type Parameters:

T - the type

Parameters:

t - the object

Returns:

the present Nillable

Throws:

NullPointerException - if t is null

absent

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

Creates a Nillable for a absent instance.

Type Parameters:

T - the type

Returns:

the absent Nillable

nil

public static <T> Nillable<T> nil(String reason)

Creates a new Nillable that is nil because of optionally supplied reason.

Type Parameters:

T - the type

Parameters:

reason - the reason (may be null)

Returns:

the nil Nillable

nil

public static <T> Nillable<T> nil()

Creates a new Nillable that is nil.

Type Parameters:

T - the type

Returns:

the nil Nillable

inapplicable

public static <T> Nillable<T> inapplicable()

Creates a new Nillable, that is nil because it is inapplicable.

Type Parameters:

T - the type

Returns:

the nil Nillable

missing

public static <T> Nillable<T> missing()

Creates a new Nillable, that is nil because it is missing.

Type Parameters:

T - the type

Returns:

the nil Nillable

template

public static <T> Nillable<T> template()

Creates a new Nillable, that is nil because it is a template value.

Type Parameters:

T - the type

Returns:

the nil Nillable

unknown

public static <T> Nillable<T> unknown()

Creates a new Nillable, that is nil because it is unknown.

Type Parameters:

T - the type

Returns:

the nil Nillable

withheld

public static <T> Nillable<T> withheld()

Creates a new Nillable, that is nil because it is withheld.

Type Parameters:

T - the type

Returns:

the nil Nillable

of

public static <T> Nillable<T> of(T obj)

Creates a new Nillable that is either present (if obj is not null), or absent.

Type Parameters:

T - the type

Parameters:

obj - the object (may be null)

Returns:

the Nillable

of

public static <T> Nillable<T> of(T obj,
                                 String reason)

Creates a new Nillable that is either present (if obj is not null), nil (if reason is not null) or absent.

Type Parameters:

T - the type

Parameters:

obj - the object (may be null)

reason - the nil reason (may be null)

Returns:

the Nillable