edu.stanford.nlp.ling
Class ValueLabel

java.lang.Object
  edu.stanford.nlp.ling.ValueLabel

All Implemented Interfaces:

Label, Serializable, Comparable<ValueLabel>

Direct Known Subclasses:

StringLabel

public abstract class ValueLabel
extends Object
implements Label, Comparable<ValueLabel>, Serializable

A ValueLabel object acts as a Label with linguistic attributes. This is an abstract class, which doesn't actually store or return anything. It returns null to any requests. However, it does stipulate that equals() and compareTo() are defined solely with respect to value(); this should not be changed by subclasses. Other fields of a ValueLabel subclass should be regarded as secondary facets (it is almost impossible to override equals in a useful way while observing the contract for equality defined for Object, in particular, that equality must by symmetric). This class is designed to be extended.

Author:

Christopher Manning

See Also:

Serialized Form

Constructor Summary

protected

ValueLabel()

Method Summary

int	compareTo(ValueLabel valueLabel) Orders by value()'s lexicographic ordering.
boolean	equals(Object obj) Equality for ValueLabels is defined in the first instance as equality of their String value().
int	hashCode() Return the hashCode of the String value providing there is one.
abstract LabelFactory	labelFactory() Returns a factory that makes Labels of the appropriate sort.
void	setFromString(String labelStr) Set the contents of this label to this String representing the complete contents of the label.
void	setValue(String value) Set the value for the label (if one is stored).
String	toString() Return a string representation of the label.
String	value() Return the value of the label (or null if none).

Methods inherited from class java.lang.Object

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

Constructor Detail

ValueLabel

protected ValueLabel()

Method Detail

value

public String value()

Return the value of the label (or null if none). The default value returned by an ValueLabel is always null

Specified by:

value in interface Label

Returns:

the value for the label

setValue

public void setValue(String value)

Set the value for the label (if one is stored).

Specified by:

setValue in interface Label

Parameters:

value - - the value for the label

toString

public String toString()

Return a string representation of the label. This will just be the value() if it is non-null, and the empty string otherwise.

Specified by:

toString in interface Label

Overrides:

toString in class Object

Returns:

The string representation

setFromString

public void setFromString(String labelStr)

Description copied from interface: Label

Set the contents of this label to this String representing the complete contents of the label. A class implementing label may throw an UnsupportedOperationException for this method (only). Typically, this method would do some appropriate decoding of the string in a way that sets multiple fields in an inverse of the toString() method.

Specified by:

setFromString in interface Label

Parameters:

labelStr - the String that translates into the content of the label

equals

public boolean equals(Object obj)

Equality for ValueLabels is defined in the first instance as equality of their String value(). Now rewritten to correctly enforce the contract of equals in Object. Equality for a ValueLabel is determined simply by String equality of its value(). Subclasses should not redefine this to include other aspects of the ValueLabel, or the contract for equals() is broken.

Overrides:

equals in class Object

Parameters:

obj - the object against which equality is to be checked

Returns:

true if this and obj are equal

hashCode

public int hashCode()

Return the hashCode of the String value providing there is one. Otherwise, returns an arbitrary constant for the case of null.

Overrides:

hashCode in class Object

compareTo

public int compareTo(ValueLabel valueLabel)

Orders by value()'s lexicographic ordering.

Specified by:

compareTo in interface Comparable<ValueLabel>

Parameters:

valueLabel - object to compare to

Returns:

result (positive if this is greater than obj)

labelFactory

public abstract LabelFactory labelFactory()

Returns a factory that makes Labels of the appropriate sort.

Specified by:

labelFactory in interface Label

Returns:

the LabelFactory