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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 | +} | |