001/*
002 * Sonar, open source software quality management tool.
003 * Copyright (C) 2008-2012 SonarSource
004 * mailto:contact AT sonarsource DOT com
005 *
006 * Sonar is free software; you can redistribute it and/or
007 * modify it under the terms of the GNU Lesser General Public
008 * License as published by the Free Software Foundation; either
009 * version 3 of the License, or (at your option) any later version.
010 *
011 * Sonar is distributed in the hope that it will be useful,
012 * but WITHOUT ANY WARRANTY; without even the implied warranty of
013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014 * Lesser General Public License for more details.
015 *
016 * You should have received a copy of the GNU Lesser General Public
017 * License along with Sonar; if not, write to the Free Software
018 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
019 */
020package org.sonar.duplications.utils;
021
022import java.util.Comparator;
023
024/**
025 * More efficient (in terms of performance) implementation of a String comparator.
026 * Speed is gained by using hash code as a primary comparison attribute, which is cached for String.
027 * Be aware that this ordering is not lexicographic, however stable.
028 */
029public final class FastStringComparator implements Comparator<String> {
030
031  public static final FastStringComparator INSTANCE = new FastStringComparator();
032
033  /**
034   * Compares two strings (not lexicographically).
035   */
036  public int compare(String s1, String s2) {
037    if (s1 == s2) { // NOSONAR false-positive: Compare Objects With Equals
038      return 0;
039    }
040    int h1 = s1.hashCode();
041    int h2 = s2.hashCode();
042    if (h1 < h2) {
043      return -1;
044    } else if (h1 > h2) {
045      return 1;
046    } else {
047      return s1.compareTo(s2);
048    }
049  }
050
051  /**
052   * Enforce use of a singleton instance.
053   */
054  private FastStringComparator() {
055  }
056
057}