/*
* Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* The Original Code is HAT. The Initial Developer of the
* Original Code is Bill Foote, with contributions from others
* at JavaSoft/Sun.
*/
package com.sun.tools.hat.internal.util;
import java.util.*;
/**
* A singleton utility class that sorts an array of objects.
* <p>
* Use:
* <pre>
*
* Stuff[] arr = ...;
* ArraySorter.sort(arr, new Comparer() {
* public int compare(Object lhs, Object rhs) {
* return ((String) lhs).compareTo((String) rhs);
* }
* });
* </pre>
*
* @author Bill Foote
*/
public class ArraySorter {
/**
* Sort the given array, using c for comparison
**/
static public void sort(Object[] arr, Comparer c) {
quickSort(arr, c, 0, arr.length-1);
}
/**
* Sort an array of strings, using String.compareTo()
**/
static public void sortArrayOfStrings(Object[] arr) {
sort(arr, new Comparer() {
public int compare(Object lhs, Object rhs) {
return ((String) lhs).compareTo((String) rhs);
}
});
}
static private void swap(Object[] arr, int a, int b) {
Object tmp = arr[a];
arr[a] = arr[b];
arr[b] = tmp;
}
//
// Sorts arr between from and to, inclusive. This is a quick, off-the-top-
// of-my-head quicksort: I haven't put any thought into optimizing it.
// I _did_ put thought into making sure it's safe (it will always
// terminate). Worst-case it's O(n^2), but it will usually run in
// in O(n log n). It's well-behaved if the list is already sorted,
// or nearly so.
//
static private void quickSort(Object[] arr, Comparer c, int from, int to) {
if (to <= from)
return;
int mid = (from + to) / 2;
if (mid != from)
swap(arr, mid, from);
Object pivot = arr[from]; // Simple-minded, but reasonable
int highestBelowPivot = from - 1;
int low = from+1;
int high = to;
// We now move low and high toward each other, maintaining the
// invariants:
// arr[i] <= pivot for all i < low
// arr[i] > pivot for all i > high
// As long as these invariants hold, and every iteration makes
// progress, we are safe.
while (low <= high) {
int cmp = c.compare(arr[low], pivot);
if (cmp <= 0) { // arr[low] <= pivot
if (cmp < 0) {
highestBelowPivot = low;
}
low++;
} else {
int c2;
for (;;) {
// arr[high] > pivot:
c2 = c.compare(arr[high], pivot);
if (c2 > 0) {
high--;
if (low > high) {
break;
}
} else {
break;
}
}
// At this point, low is never == high, BTW
if (low <= high) {
swap(arr, low, high);
if (c2 < 0) {
highestBelowPivot = low;
}
low++;
high--;
}
}
}
// At this point, low == high+1
// Now we just need to sort from from..highestBelowPivot
// and from high+1..to
if (highestBelowPivot > from) {
// pivot == pivot, so ensure algorithm terminates
swap(arr, from, highestBelowPivot);
quickSort(arr, c, from, highestBelowPivot-1);
}
quickSort(arr, c, high+1, to);
}
}