uk.ac.starlink.ttools.jel

Class FixedConstant<T>

java.lang.Object

uk.ac.starlink.ttools.jel.FixedConstant<T>

All Implemented Interfaces:

Constant<T>

public class FixedConstant<T>
extends Object
implements Constant<T>

Constant implementation which always has the same value.

Since:

10 Dec 2007

Author:

Mark Taylor

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
static <T> FixedConstant<T>	createConstant(T value) Constructs a constant with a given value.
Class<T>	getContentClass() Returns a class of which this object's value will be an instance.
T	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(T value,
                     Class<T> clazz)

Constructs a constant with a given value and class.

Parameters:

clazz - content class

value - value

Method Detail

getContentClass

public Class<T> 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<T>

Returns:

content class

getValue

public T getValue()

Description copied from interface: Constant

Returns this object's value. Not necessarily always the same.

Specified by:

getValue in interface Constant<T>

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<T>

Returns:

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

createConstant

public static <T> FixedConstant<T> createConstant(T value)

Constructs a constant with a given value. The constant parameterised type is the runtime type of the supplied value.

Parameters:

value - constant value

Returns:

new constant