lp.struct
Class LpVariable

java.lang.Object
  lp.struct.LpAbstractStructureUnit
      lp.struct.LpVariable

All Implemented Interfaces:

LpStructureUnit, LpTerm

public class LpVariable
extends LpAbstractStructureUnit
implements LpTerm

Represents a variable in logic programming. Variables are, together with function symbols and constants (see LpFunction and LpConstant) building units of terms (see LpTerm). Each variable has a unique non-empty name.

Version:

1.0.0

Author:

Martin Slota

See Also:

LpTerm

Field Summary

private String	name This variable's name.
private static Map<String,LpVariable>	pool A pool of instances of this immutable class.

Fields inherited from class lp.struct.LpAbstractStructureUnit

TO_STRING_BUFFER

Constructor Summary

protected

LpVariable(String name) Creates a new instance of LpVariable with the given name.

Method Summary

void	accept(LpStructureUnitVisitor visitor) Accepts LpStructureUnitVisitor instance, i.e. calls visitor.visit(this).
boolean	equals(Object obj) Returns true if and only if obj is a LpVariable instance, its name is equal to this variable's name as defined by String.equals(Object),
static LpVariable	getInstance(String name) Returns an instance of LpVariable with the given name.
String	getName() Returns this variable's name, the same that was given to the constructor.
int	hashCode() Overriden in order to maintain the general contract of Object.hashCode().

Methods inherited from class lp.struct.LpAbstractStructureUnit

toString, toUnmodifiableList, toUnmodifiableSet

Methods inherited from class java.lang.Object

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

Field Detail

pool

private static final Map<String,LpVariable> pool

A pool of instances of this immutable class. The getInstance(String) method first looks here for the requested instances and if it is forced to create a new one, it is added to this pool.

name

private final String name

This variable's name.

Constructor Detail

LpVariable

protected LpVariable(String name)

Creates a new instance of LpVariable with the given name.

Parameters:

name - the new variable's name

Throws:

IllegalArgumentException - if name is null or an empty string

Method Detail

getInstance

public static LpVariable getInstance(String name)

Returns an instance of LpVariable with the given name.

Parameters:

name - the requested variable's name

Throws:

IllegalArgumentException - if name is null or an empty string

getName

public String getName()

Returns this variable's name, the same that was given to the constructor.

Returns:

the name of this variable

accept

public void accept(LpStructureUnitVisitor visitor)

Accepts LpStructureUnitVisitor instance, i.e. calls visitor.visit(this).

Specified by:

accept in interface LpStructureUnit

Parameters:

visitor - the visitor to accept

equals

public boolean equals(Object obj)

Returns true if and only if

1. obj is a LpVariable instance,
2. its name is equal to this variable's name as defined by String.equals(Object),

Specified by:

equals in interface LpTerm

Overrides:

equals in class Object

Parameters:

obj - the object to compare with

Returns:

true if this object is equal to obj according to the description above, and false otherwise

See Also:

String.equals(Object), LpTerm.equals(Object)

hashCode

public int hashCode()

Overriden in order to maintain the general contract of Object.hashCode().

Specified by:

hashCode in interface LpTerm

Overrides:

hashCode in class Object

Returns:

the hash of this object

See Also:

String.hashCode(), LpTerm.equals(Object)