org.apache.commons.functor.core
Class IsNull<A>

java.lang.Object
  org.apache.commons.functor.core.IsNull<A>

Type Parameters:

A - the argument type.

All Implemented Interfaces:

Serializable, Functor, UnaryFunctor<A>, UnaryPredicate<A>

public final class IsNull<A>
extends Object
implements UnaryPredicate<A>, Serializable

Tests true iff its argument is null.

Version:

$Revision: 1160407 $ $Date: 2011-08-22 22:03:21 +0200 (Mon, 22 Aug 2011) $

Author:

Rodney Waldhoff

See Also:

Serialized Form

Field Summary

static IsNull<Object>	INSTANCE Basic IsNull instance.
static BinaryPredicate<Object,Object>	LEFT Left-handed BinaryPredicate.
static BinaryPredicate<Object,Object>	RIGHT Right-handed BinaryPredicate.

Constructor Summary

IsNull()
Create a new IsNull.

Method Summary

boolean	equals(Object that) Indicates whether some other object is "equal to" this functor.
int	hashCode() Returns a hash code for this functor adhering to the general Object.hashCode contract.
static <T> IsNull<T>	instance() Get an IsNull instance.
static <A> BinaryPredicate<A,Object>	left() Get a BinaryPredicate that matches if the left argument is null.
static <A> BinaryPredicate<Object,A>	right() Get a BinaryPredicate that matches if the right argument is null.
boolean	test(A obj) Evaluate this predicate.
String	toString() Returns a human readable description of this functor.

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final IsNull<Object> INSTANCE

Basic IsNull instance.

LEFT

public static final BinaryPredicate<Object,Object> LEFT

Left-handed BinaryPredicate.

RIGHT

public static final BinaryPredicate<Object,Object> RIGHT

Right-handed BinaryPredicate.

Constructor Detail

IsNull

public IsNull()

Create a new IsNull.

Method Detail

test

public boolean test(A obj)

Evaluate this predicate.

Specified by:

test in interface UnaryPredicate<A>

Parameters:

obj - the A object to test

Returns:

the result of this test

equals

public boolean equals(Object that)

Indicates whether some other object is "equal to" this functor. This method must adhere to general Object.equals contract. Additionally, this method can return true only if the specified Object implements the same functor interface and is known to produce the same results and/or side-effects for the same arguments (if any).

While implementators are strongly encouraged to override the default Object implementation of this method, note that the default Object implementation does in fact adhere to the functor equals contract.

Specified by:

equals in interface Functor

Overrides:

equals in class Object

Parameters:

that - the object to compare this functor to

Returns:

true iff the given object implements this functor interface, and is known to produce the same results and/or side-effects for the same arguments (if any).

See Also:

Functor.hashCode()

hashCode

public int hashCode()

Returns a hash code for this functor adhering to the general Object.hashCode contract. Implementators are strongly encouraged but not strictly required to override the default Object implementation of this method.

Specified by:

hashCode in interface Functor

Overrides:

hashCode in class Object

Returns:

a hash code for this functor

See Also:

Functor.equals(java.lang.Object)

toString

public String toString()

Returns a human readable description of this functor. Implementators are strongly encouraged but not strictly required to override the default Object implementation of this method.

Specified by:

toString in interface Functor

Overrides:

toString in class Object

Returns:

a human readable description of this functor

instance

public static <T> IsNull<T> instance()

Get an IsNull instance.

Type Parameters:

T - the predicate argument type.

Returns:

IsNull

left

public static <A> BinaryPredicate<A,Object> left()

Get a BinaryPredicate that matches if the left argument is null.

Type Parameters:

A - the left BinaryPredicate argument type.

Returns:

BinaryPredicate

right

public static <A> BinaryPredicate<Object,A> right()

Get a BinaryPredicate that matches if the right argument is null.

Type Parameters:

A - the right BinaryPredicate argument type.

Returns:

BinaryPredicate