/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.configuration2.interpol;

 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/**
 * <p>
 * A simple dummy {@code Lookup} implementation.
 * </p>
 * <p>
 * This implementation always returns <b>null</b> for a passed in variable
 * indicating that it cannot resolve that variable. This is useful for instance
 * as an application of the <em>null object</em> pattern.
 * </p>
 * <p>
 * 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.
 * </p>
 *
 * @since 2.0
 */
public enum DummyLookup implements Lookup
{
    
The single instance of this class. /** The single instance of this class. */
    INSTANCE;

    
{@inheritDoc} This implementation always returns null.
/**
     * {@inheritDoc} This implementation always returns <b>null</b>.
     */
    @Override
    public Object lookup(final String variable)
    {
        return null;
    }
}