Package org.apache.commons.configuration2.interpol

Enum DummyLookup

java.lang.Object

java.lang.Enum<DummyLookup>

org.apache.commons.configuration2.interpol.DummyLookup

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<DummyLookup>, Lookup

public enum DummyLookup
extends java.lang.Enum<DummyLookup>
implements Lookup

A simple dummy Lookup implementation.

This implementation always returns null for a passed in variable indicating that it cannot resolve that variable. This is useful for instance as an application of the null object pattern.

This class does not define any state, therefore a single instance can be shared. To enforce usage of only a single instance this class is actually an enumeration.

Since:

2.0

Version:

$Id: DummyLookup.java 1624601 2014-09-12 18:04:36Z oheger $

Enum Constant Summary

Enum Constants

Enum Constant	Description
INSTANCE	The single instance of this class.

Method Summary

Modifier and Type	Method	Description
java.lang.Object	lookup(java.lang.String variable)	Looks up the value of the specified variable.
static DummyLookup	valueOf(java.lang.String name)	Returns the enum constant of this type with the specified name.
static DummyLookup[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

INSTANCE

public static final DummyLookup INSTANCE

The single instance of this class.

Method Detail

values

public static DummyLookup[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (DummyLookup c : DummyLookup.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static DummyLookup valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null

lookup

public java.lang.Object lookup(java.lang.String variable)

Looks up the value of the specified variable. This method is called by ConfigurationInterpolator with the variable name extracted from the expression to interpolate (i.e. the prefix name has already been removed). A concrete implementation has to return the value of this variable or null if the variable name is unknown. This implementation always returns null.

Specified by:

lookup in interface Lookup

Parameters:

variable - the name of the variable to be resolved

Returns:

the value of this variable or null