uk.ac.starlink.ttools.jel

Class FixedConstant

java.lang.Object

uk.ac.starlink.ttools.jel.FixedConstant

All Implemented Interfaces:

Constant

public class FixedConstant
extends Object
implements Constant

Constant implementation which always has the same value.

Since:

10 Dec 2007

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
FixedConstant(Object value) Constructs a constant with a given value.
FixedConstant(Object value, Class<?> clazz) Constructs a constant with a given value and class.

Method Summary

Modifier and Type	Method and Description
Class<?>	getContentClass() Returns a class of which this object's value will be an instance.
Object	getValue() Returns this object's value.
boolean	requiresRowIndex() Indicates whether evaluation of this constant needs to know the row index.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FixedConstant

public FixedConstant(Object value,
                     Class<?> clazz)

Constructs a constant with a given value and class.

Parameters:

clazz - content class

value - value

FixedConstant

public FixedConstant(Object value)

Constructs a constant with a given value. The class is the class of value.

Parameters:

value - value

Method Detail

getContentClass

public Class<?> getContentClass()

Description copied from interface: Constant

Returns a class of which this object's value will be an instance.

Specified by:

getContentClass in interface Constant

Returns:

content class

getValue

public Object getValue()

Description copied from interface: Constant

Returns this object's value. Not necessarily always the same. Must be an instance of Constant.getContentClass() (or null).

Specified by:

getValue in interface Constant

Returns:

value

requiresRowIndex

public boolean requiresRowIndex()

Description copied from interface: Constant

Indicates whether evaluation of this constant needs to know the row index. If executing Constant.getValue() may result in a call to StarTableJELRowReader.getCurrentRow(), this method must return true.

Specified by:

requiresRowIndex in interface Constant

Returns:

true if evaluating this constant needs or may need to know the current row index