NilExpression (Geotools modules 31-SNAPSHOT API)

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

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	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