001/*-------------------------------------------------------------------------+
002|                                                                          |
003| Copyright 2005-2011 The ConQAT Project                                   |
004|                                                                          |
005| Licensed under the Apache License, Version 2.0 (the "License");          |
006| you may not use this file except in compliance with the License.         |
007| You may obtain a copy of the License at                                  |
008|                                                                          |
009|    http://www.apache.org/licenses/LICENSE-2.0                            |
010|                                                                          |
011| Unless required by applicable law or agreed to in writing, software      |
012| distributed under the License is distributed on an "AS IS" BASIS,        |
013| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
014| See the License for the specific language governing permissions and      |
015| limitations under the License.                                           |
016+-------------------------------------------------------------------------*/
017package org.conqat.lib.commons.collections;
018
019import java.util.HashMap;
020import java.util.Map;
021
022/**
023 * A map implementation of a map using string keys. This is based on a hybrid
024 * map which uses an {@link ArrayBackedStringMap} while only a small number of
025 * keys are present and switches to a {@link HashMap} after a certain size has
026 * been reached.
027 * 
028 * @author hummelb
029 */
030public class MemoryEfficientStringMap<V> extends HybridMapBase<String, V> {
031
032        /** The maximal size of the map before switching is performed. */
033        private static final int SWITCHING_SIZE = 16;
034
035        /** Constructor. */
036        public MemoryEfficientStringMap() {
037                super(new ArrayBackedStringMap<V>(4));
038        }
039
040        /** Constructor. */
041        public MemoryEfficientStringMap(Map<? extends String, ? extends V> map) {
042                this();
043                putAll(map);
044        }
045
046        /** {@inheritDoc} */
047        @Override
048        protected Map<String, V> obtainNewMap() {
049                return new HashMap<String, V>();
050        }
051
052        /** {@inheritDoc} */
053        @Override
054        protected boolean shouldSwitch(Map<String, V> map) {
055                return map.size() == SWITCHING_SIZE && map instanceof ArrayBackedMap<?, ?>;
056        }
057}