ConstantExpression (Geotools modules 28-SNAPSHOT API)

Object
- ConstantExpression

All Implemented Interfaces:

Cloneable, Expression, Literal

Direct Known Subclasses:

OverlapBehavior
```
public class ConstantExpression
extends Object
implements Literal, Cloneable
```
The Expression class is not immutable!
However we do have a need for immutable literal expressions when defining our API for SLD, and any other standards based on Expression.

Author:

Jody Garnett, Refractions Research

Field Summary

Fields
Modifier and Type	Field and Description
`static ConstantExpression`	`BLACK`
`static ConstantExpression`	`NULL`
`static ConstantExpression`	`ONE`
`static ConstantExpression`	`TWO`
`static ConstantExpression`	`UNNAMED`
`static ConstantExpression`	`ZERO`

Fields inherited from interface Expression
NIL

Constructor Summary

Constructors
Modifier Constructor and Description

protected ConstantExpression(Object value)

protected ConstantExpression(short type, Object value)

Constructors
Modifier	Constructor and Description
`protected`	`ConstantExpression(Object value)`
`protected`	`ConstantExpression(short type, Object value)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Object`	`accept(ExpressionVisitor visitor, Object extraData)` Accepts a visitor.
`protected Object`	`clone()`
`static ConstantExpression`	`color(Color color)` Encode provided color as a String
`static ConstantExpression`	`constant(double number)`
`static ConstantExpression`	`constant(int number)`
`static ConstantExpression`	`constant(Object value)`
`boolean`	`equals(Object obj)`
`Object`	`evaluate(Object object)` Evaluates the given expression based on the content of the given object.
`<T> T`	`evaluate(Object object, Class<T> context)` Evaluates the given expressoin based on the content of the given object and the context type.
`Object`	`evaluate(SimpleFeature feature)`
`short`	`getType()`
`Object`	`getValue()` Returns the constant value held by this object.
`int`	`hashCode()`
`void`	`setValue(Object constant)`
`String`	`toString()`

Methods inherited from class Object
finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - NULL
```
public static final ConstantExpression NULL
```
  - BLACK
```
public static final ConstantExpression BLACK
```
  - ZERO
```
public static final ConstantExpression ZERO
```
  - ONE
```
public static final ConstantExpression ONE
```
  - TWO
```
public static final ConstantExpression TWO
```
  - UNNAMED
```
public static final ConstantExpression UNNAMED
```
- Constructor Detail
  - ConstantExpression
```
protected ConstantExpression(Object value)
```
  - ConstantExpression
```
protected ConstantExpression(short type,
                             Object value)
```
- Method Detail
  - evaluate
```
public Object evaluate(SimpleFeature feature)
```
  - evaluate
```
public Object evaluate(Object object)
```
    Description copied from interface: Expression
    
    Evaluates the given expression based on the content of the given object.
    
    Specified by:
    
    evaluate in interface Expression
    
    Returns:
    
    computed value
  - evaluate
```
public <T> T evaluate(Object object,
                      Class<T> context)
```
    Description copied from interface: Expression
    Evaluates the given expressoin based on the content of the given object and the context type.
    The context parameter is used to control the type of the result of the expression. A particular expression may not be able to evaluate to an instance of context. Therefore to be safe calling code should do a null check on the return value of this method, and call Expression.evaluate(Object) if neccessary. Example:
```
  Object input = ...;
  String result = expression.evaluate( input, String.class );
  if ( result == null ) {
     result = expression.evalute( input ).toString();
  }
  ...
 
```
    Implementations that can not return a result as an instance of context should return 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.
  - getValue
```
public Object getValue()
```
    Description copied from interface: Literal
    
    Returns the constant value held by this object.
    
    Specified by:
    
    getValue in interface Literal
  - setValue
```
public void setValue(Object constant)
```
  - getType
```
public short getType()
```
  - accept
```
public Object accept(ExpressionVisitor visitor,
                     Object extraData)
```
    Description copied from interface: Expression
    Accepts a visitor. Subclasses must implement with a method whose content is the following:
```
return visitor.visit(this, extraData);
```
    Specified by:
    
    accept in interface Expression
  - clone
```
protected Object clone()
                throws CloneNotSupportedException
```
    Overrides:
    
    clone in class Object
    
    Throws:
    
    CloneNotSupportedException
  - equals
```
public boolean equals(Object obj)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - color
```
public static ConstantExpression color(Color color)
```
    Encode provided color as a String
  - constant
```
public static ConstantExpression constant(double number)
```
  - constant
```
public static ConstantExpression constant(int number)
```
  - constant
```
public static ConstantExpression constant(Object value)
```

Class ConstantExpression

Field Summary

Fields inherited from interface Expression

Constructor Summary

Method Summary

Methods inherited from class Object

Field Detail

NULL

BLACK

ZERO

ONE

TWO

UNNAMED

Constructor Detail

ConstantExpression

ConstantExpression

Method Detail

evaluate

evaluate

evaluate

getValue

setValue

getType

accept

clone

equals

hashCode

toString

color

constant

constant

constant