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| 1 | /* | ||
| 2 | * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | |||
| 27 | /* | ||
| 28 | * The Original Code is HAT. The Initial Developer of the | ||
| 29 | * Original Code is Bill Foote, with contributions from others | ||
| 30 | * at JavaSoft/Sun. | ||
| 31 | */ | ||
| 32 | |||
| 33 | package com.sun.tools.hat.internal.util; | ||
| 34 | import java.util.*; | ||
| 35 | |||
| 36 | /** | ||
| 37 | * A singleton utility class that sorts an array of objects. | ||
| 38 | * <p> | ||
| 39 | * Use: | ||
| 40 | * <pre> | ||
| 41 | * | ||
| 42 | * Stuff[] arr = ...; | ||
| 43 | * ArraySorter.sort(arr, new Comparer() { | ||
| 44 | * public int compare(Object lhs, Object rhs) { | ||
| 45 | * return ((String) lhs).compareTo((String) rhs); | ||
| 46 | * } | ||
| 47 | * }); | ||
| 48 | * </pre> | ||
| 49 | * | ||
| 50 | * @author Bill Foote | ||
| 51 | */ | ||
| 52 | |||
| 53 | public class ArraySorter { | ||
| 54 | |||
| 55 | /** | ||
| 56 | * Sort the given array, using c for comparison | ||
| 57 | **/ | ||
| 58 | static public void sort(Object[] arr, Comparer c) { | ||
| 59 | quickSort(arr, c, 0, arr.length-1); | ||
| 60 | } | ||
| 61 | |||
| 62 | |||
| 63 | /** | ||
| 64 | * Sort an array of strings, using String.compareTo() | ||
| 65 | **/ | ||
| 66 | static public void sortArrayOfStrings(Object[] arr) { | ||
| 67 | sort(arr, new Comparer() { | ||
| 68 | public int compare(Object lhs, Object rhs) { | ||
| 69 | return ((String) lhs).compareTo((String) rhs); | ||
| 70 | } | ||
| 71 | }); | ||
| 72 | } | ||
| 73 | |||
| 74 | |||
| 75 | static private void swap(Object[] arr, int a, int b) { | ||
| 76 | Object tmp = arr[a]; | ||
| 77 | arr[a] = arr[b]; | ||
| 78 | arr[b] = tmp; | ||
| 79 | } | ||
| 80 | |||
| 81 | // | ||
| 82 | // Sorts arr between from and to, inclusive. This is a quick, off-the-top- | ||
| 83 | // of-my-head quicksort: I haven't put any thought into optimizing it. | ||
| 84 | // I _did_ put thought into making sure it's safe (it will always | ||
| 85 | // terminate). Worst-case it's O(n^2), but it will usually run in | ||
| 86 | // in O(n log n). It's well-behaved if the list is already sorted, | ||
| 87 | // or nearly so. | ||
| 88 | // | ||
| 89 | static private void quickSort(Object[] arr, Comparer c, int from, int to) { | ||
| 90 | if (to <= from) | ||
| 91 | return; | ||
| 92 | int mid = (from + to) / 2; | ||
| 93 | if (mid != from) | ||
| 94 | swap(arr, mid, from); | ||
| 95 | Object pivot = arr[from]; // Simple-minded, but reasonable | ||
| 96 | int highestBelowPivot = from - 1; | ||
| 97 | int low = from+1; | ||
| 98 | int high = to; | ||
| 99 | // We now move low and high toward each other, maintaining the | ||
| 100 | // invariants: | ||
| 101 | // arr[i] <= pivot for all i < low | ||
| 102 | // arr[i] > pivot for all i > high | ||
| 103 | // As long as these invariants hold, and every iteration makes | ||
| 104 | // progress, we are safe. | ||
| 105 | while (low <= high) { | ||
| 106 | int cmp = c.compare(arr[low], pivot); | ||
| 107 | if (cmp <= 0) { // arr[low] <= pivot | ||
| 108 | if (cmp < 0) { | ||
| 109 | highestBelowPivot = low; | ||
| 110 | } | ||
| 111 | low++; | ||
| 112 | } else { | ||
| 113 | int c2; | ||
| 114 | for (;;) { | ||
| 115 | // arr[high] > pivot: | ||
| 116 | c2 = c.compare(arr[high], pivot); | ||
| 117 | if (c2 > 0) { | ||
| 118 | high--; | ||
| 119 | if (low > high) { | ||
| 120 | break; | ||
| 121 | } | ||
| 122 | } else { | ||
| 123 | break; | ||
| 124 | } | ||
| 125 | } | ||
| 126 | // At this point, low is never == high, BTW | ||
| 127 | if (low <= high) { | ||
| 128 | swap(arr, low, high); | ||
| 129 | if (c2 < 0) { | ||
| 130 | highestBelowPivot = low; | ||
| 131 | } | ||
| 132 | low++; | ||
| 133 | high--; | ||
| 134 | } | ||
| 135 | } | ||
| 136 | } | ||
| 137 | // At this point, low == high+1 | ||
| 138 | // Now we just need to sort from from..highestBelowPivot | ||
| 139 | // and from high+1..to | ||
| 140 | if (highestBelowPivot > from) { | ||
| 141 | // pivot == pivot, so ensure algorithm terminates | ||
| 142 | swap(arr, from, highestBelowPivot); | ||
| 143 | quickSort(arr, c, from, highestBelowPivot-1); | ||
| 144 | } | ||
| 145 | quickSort(arr, c, high+1, to); | ||
| 146 | } | ||
| 147 | } | ||