001 /*--------------------------------------------------------------------------+ 002 $Id: FastStringComparator.java 28495 2010-06-22 09:24:54Z deissenb $ 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.string; 019 020 import java.util.Comparator; 021 022 /** 023 * This is a more efficient implementation of a String comparator. While the 024 * comparison order is stable, there is no guarantee that is is lexicographic. 025 * The additional speed is gained by using the hash code as primary comparison 026 * attribute. As the hash code is cached by the string object, its access is 027 * very cheap even for long strings. 028 * 029 * @author hummelb 030 * @author $Author: deissenb $ 031 * @version $Rev: 28495 $ 032 * @levd.rating GREEN Hash: 377662AA56158F4D3E09C59056FBDEED 033 */ 034 public class FastStringComparator implements Comparator<String> { 035 036 /** Singleton instance. */ 037 public static final FastStringComparator INSTANCE = new FastStringComparator(); 038 039 /** {@inheritDoc} */ 040 @Override 041 public int compare(String s0, String s1) { 042 if (s0 == s1) { 043 return 0; 044 } 045 int hash0 = s0.hashCode(); 046 int hash1 = s1.hashCode(); 047 if (hash0 < hash1) { 048 return -1; 049 } 050 if (hash0 > hash1) { 051 return 1; 052 } 053 054 return s0.compareTo(s1); 055 } 056 }