org.opengis.filter.expression
Class NilExpression

Object
  extended by NilExpression
All Implemented Interfaces:
Serializable, Expression

public final class NilExpression
extends Object
implements Expression, Serializable

Placeholder class used to represent a NIL expression, evaluates to null. This placeholder class allows data structures to avoid the use of null. Please note that Expression.NIL is not considered a Literal with value null (since the literal may have its value changed).

Author:
Jody Garnett (Refractions Research, Inc.), Martin Desruisseaux (Geomatys)
See Also:
Serialized Form

Field Summary
 
Fields inherited from interface Expression
NIL
 
Method Summary
 Object accept(ExpressionVisitor visitor, Object extraData)
          Accepts a visitor.
 Object evaluate(Object object)
          Returns null.
<T> T
evaluate(Object object, Class<T> context)
          Returns null.
 String toString()
          Returns a string representation of this expression.
 
Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Method Detail

accept

public Object accept(ExpressionVisitor visitor,
                     Object extraData)
Accepts a visitor.

Specified by:
accept in interface Expression

evaluate

public Object evaluate(Object object)
Returns null.

Specified by:
evaluate in interface Expression

evaluate

public <T> T evaluate(Object object,
                      Class<T> context)
Returns null.

Specified by:
evaluate in interface Expression
Type Parameters:
T - The type of the returned object.
Parameters:
object - The object to evaluate the expression against.
context - The type of the resulting value of the expression.
Returns:
Evaluates the given expression based on the content of the given object an an instance of context.

toString

public String toString()
Returns a string representation of this expression.

Overrides:
toString in class Object


Copyright © 1996-2014 Geotools. All Rights Reserved.