lp.unit
Class EmptyProgram

java.lang.Object
  lp.unit.EmptyProgram

All Implemented Interfaces:

Iterable<LpRule>, Collection<LpRule>, Set<LpRule>, LogicProgram

 class EmptyProgram
extends Object
implements LogicProgram

An efficient implementation of an empty logic program that is immutable. May be useful in some cases :o)

Version:

1.0.0

Author:

Martin Slota

See Also:

LogicProgram, DynamicLogicProgram

Field Summary

private static Object[]	AS_ARRAY Empty array used to return the program as an of rules.
private static EmptyProgram	instance The singleton instance.
private static Iterator<LpRule>	ITR A static iterator over an empty collection of rules.

Constructor Summary

private

EmptyProgram() A private constructor because this class is a singleton.

Method Summary

boolean	add(LpRule r) Throws an UnsupportedOperationException.
boolean	addAll(Collection<? extends LpRule> c) Throws an UnsupportedOperationException.
void	clear() Throws an UnsupportedOperationException.
boolean	contains(Object o) Returns false.
boolean	containsAll(Collection<?> c) Returns the same as c.isEmpty().
boolean	equals(Object obj) Returns true iff obj implements the LogicProgram interface and contains no rules.
LpRule	get(int index) Throws an IndexOutOfBoundsException.
static EmptyProgram	getInstance() Returns the singleton instance.
int	hashCode() Returns the hash code of an empty set.
boolean	isEmpty() Returns true.
boolean	isGround() Returns true.
Iterator<LpRule>	iterator() Returns the iterator for this empty collection.
boolean	remove(Object o) Throws an UnsupportedOperationException.
boolean	removeAll(Collection<?> c) Throws an UnsupportedOperationException.
boolean	retainAll(Collection<?> c) Throws an UnsupportedOperationException.
int	size() Returns 0.
Object[]	toArray() Returns an empty array.
<T> T[]	toArray(T[] a) Returns an empty array.
String	toString() Returns the string "[]".

Methods inherited from class java.lang.Object

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

Field Detail

instance

private static EmptyProgram instance

The singleton instance.

ITR

private static final Iterator<LpRule> ITR

A static iterator over an empty collection of rules.

AS_ARRAY

private static final Object[] AS_ARRAY

Empty array used to return the program as an of rules.

Constructor Detail

EmptyProgram

private EmptyProgram()

A private constructor because this class is a singleton.

Method Detail

getInstance

public static EmptyProgram getInstance()

Returns the singleton instance.

Returns:

the singleton instance of EmptyProgram

size

public int size()

Returns 0.

Specified by:

size in interface Collection<LpRule>

Specified by:

size in interface Set<LpRule>

Returns:

0

isEmpty

public boolean isEmpty()

Returns true.

Specified by:

isEmpty in interface Collection<LpRule>

Specified by:

isEmpty in interface Set<LpRule>

Returns:

true

contains

public boolean contains(Object o)

Returns false.

Specified by:

contains in interface Collection<LpRule>

Specified by:

contains in interface Set<LpRule>

Parameters:

o - the object to look for (cannot be contained in an empty collection)

Returns:

false

iterator

public Iterator<LpRule> iterator()

Returns the iterator for this empty collection.

Specified by:

iterator in interface Iterable<LpRule>

Specified by:

iterator in interface Collection<LpRule>

Specified by:

iterator in interface Set<LpRule>

Returns:

the iterator for this empty collection

toArray

public Object[] toArray()

Returns an empty array.

Specified by:

toArray in interface Collection<LpRule>

Specified by:

toArray in interface Set<LpRule>

Returns:

an empty array

toArray

public <T> T[] toArray(T[] a)

Returns an empty array.

Specified by:

toArray in interface Collection<LpRule>

Specified by:

toArray in interface Set<LpRule>

Returns:

an empty array

add

public boolean add(LpRule r)

Throws an UnsupportedOperationException.

Specified by:

add in interface Collection<LpRule>

Specified by:

add in interface Set<LpRule>

Parameters:

r - the rule to add

Throws:

UnsupportedOperationException - always

remove

public boolean remove(Object o)

Throws an UnsupportedOperationException.

Specified by:

remove in interface Collection<LpRule>

Specified by:

remove in interface Set<LpRule>

Parameters:

o - the rule to remove

Throws:

UnsupportedOperationException - always

containsAll

public boolean containsAll(Collection<?> c)

Returns the same as c.isEmpty().

Specified by:

containsAll in interface Collection<LpRule>

Specified by:

containsAll in interface Set<LpRule>

Returns:

as specified above

addAll

public boolean addAll(Collection<? extends LpRule> c)

Throws an UnsupportedOperationException.

Specified by:

addAll in interface Collection<LpRule>

Specified by:

addAll in interface Set<LpRule>

Parameters:

c - the collection of rules to add

Throws:

UnsupportedOperationException - always

removeAll

public boolean removeAll(Collection<?> c)

Throws an UnsupportedOperationException.

Specified by:

removeAll in interface Collection<LpRule>

Specified by:

removeAll in interface Set<LpRule>

Parameters:

c - the collection of rules to remove

Throws:

UnsupportedOperationException - always

retainAll

public boolean retainAll(Collection<?> c)

Throws an UnsupportedOperationException.

Specified by:

retainAll in interface Collection<LpRule>

Specified by:

retainAll in interface Set<LpRule>

Parameters:

c - the collection of rules to retain

Throws:

UnsupportedOperationException - always

get

public LpRule get(int index)

Throws an IndexOutOfBoundsException.

Specified by:

get in interface LogicProgram

Parameters:

index - the index of the rule to return

Throws:

IndexOutOfBoundsException - always

clear

public void clear()

Throws an UnsupportedOperationException.

Specified by:

clear in interface Collection<LpRule>

Specified by:

clear in interface Set<LpRule>

Throws:

UnsupportedOperationException - always

equals

public boolean equals(Object obj)

Returns true iff obj implements the LogicProgram interface and contains no rules.

Specified by:

equals in interface Collection<LpRule>

Specified by:

equals in interface Set<LpRule>

Overrides:

equals in class Object

Parameters:

obj - the object to compare with

Returns:

as specified above

hashCode

public int hashCode()

Returns the hash code of an empty set.

Specified by:

hashCode in interface Collection<LpRule>

Specified by:

hashCode in interface Set<LpRule>

Overrides:

hashCode in class Object

Returns:

the hash code of an empty set

See Also:

Collections.emptySet()

isGround

public boolean isGround()

Returns true.

Specified by:

isGround in interface LogicProgram

Returns:

true

See Also:

LpGroundDecider.isGround(LpStructureUnit)

toString

public String toString()

Returns the string "[]".

Overrides:

toString in class Object

Returns:

the string "[]"