IdentityDictionary.java

/***************************************************************************
   Copyright 2013 Emily Estes

   Licensed 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 net.metanotion.util;


/** This dictionary instance is purely utility and a suitable default for some
interesting situations. It implements the "identity map". Any key requested
for look up is returned as the value of the look up.
	@param <I> The type of values this dictionary operates on.
*/
public final class IdentityDictionary<I> implements Dictionary<I,I>  {
	/** Since this class is stateless, this is provided for convenience. */
	public static final IdentityDictionary INSTANCE = new IdentityDictionary();
	@Override public I get(I key) { return key; }
}