org.opengis.filter.expression

Class NilExpression

Object

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

Modifier and Type	Method and Description
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

Returns:

computed value

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