001 /*--------------------------------------------------------------------------+ 002 $Id: MemoryEfficientStringMap.java 29399 2010-07-27 15:03:17Z juergens $ 003 | | 004 | Copyright 2005-2010 Technische Universitaet Muenchen | 005 | | 006 | Licensed under the Apache License, Version 2.0 (the "License"); | 007 | you may not use this file except in compliance with the License. | 008 | You may obtain a copy of the License at | 009 | | 010 | http://www.apache.org/licenses/LICENSE-2.0 | 011 | | 012 | Unless required by applicable law or agreed to in writing, software | 013 | distributed under the License is distributed on an "AS IS" BASIS, | 014 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | 015 | See the License for the specific language governing permissions and | 016 | limitations under the License. | 017 +--------------------------------------------------------------------------*/ 018 package edu.tum.cs.commons.collections; 019 020 import java.util.HashMap; 021 import java.util.Map; 022 023 /** 024 * A map implementation of a map using string keys. This is based on a hybrid 025 * map which uses an {@link ArrayBackedStringMap} while only a small number of 026 * keys are present and switches to a {@link HashMap} after a certain size has 027 * been reached. 028 * 029 * @author hummelb 030 * @author $Author: juergens $ 031 * @version $Rev: 29399 $ 032 * @levd.rating GREEN Hash: B82C7BCF35689181816346E57A25D854 033 */ 034 public class MemoryEfficientStringMap<V> extends HybridMapBase<String, V> { 035 036 /** The maximal size of the map before switching is performed. */ 037 private static final int SWITCHING_SIZE = 16; 038 039 /** Constructor. */ 040 public MemoryEfficientStringMap() { 041 super(new ArrayBackedStringMap<V>(4)); 042 } 043 044 /** Constructor. */ 045 public MemoryEfficientStringMap(Map<? extends String, ? extends V> map) { 046 this(); 047 putAll(map); 048 } 049 050 /** {@inheritDoc} */ 051 @Override 052 protected Map<String, V> obtainNewMap() { 053 return new HashMap<String, V>(); 054 } 055 056 /** {@inheritDoc} */ 057 @Override 058 protected boolean shouldSwitch(Map<String, V> map) { 059 return map.size() == SWITCHING_SIZE 060 && map instanceof ArrayBackedMap<?, ?>; 061 } 062 }