corda/classpath/java/util/Arrays.java
Johannes Schindelin 605701e40a Replace Arrays.sort() with an efficient sort algorithm
This change reuses the existing insertion sort (which was previously what
Arrays.sort() executed) in a full intro sort pipeline.

The implementation is based on the Musser paper on intro sort (Musser,
David R. "Introspective sorting and selection algorithms." Softw., Pract.
Exper. 27.8 (1997): 983-993.) and Wikipedia's current description of the
heap sort: http://en.wikipedia.org/wiki/Heapsort.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2013-11-04 00:27:04 -06:00

352 lines
8.2 KiB
Java

/* Copyright (c) 2008-2013, Avian Contributors
Permission to use, copy, modify, and/or distribute this software
for any purpose with or without fee is hereby granted, provided
that the above copyright notice and this permission notice appear
in all copies.
There is NO WARRANTY for this software. See license.txt for
details. */
package java.util;
public class Arrays {
private Arrays() { }
public static String toString(Object[] a) {
return asList(a).toString();
}
public static String toString(boolean[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
public static String toString(byte[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
public static String toString(short[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
public static String toString(int[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
public static String toString(long[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
public static String toString(float[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
public static String toString(double[] a) {
if (a == null) {
return "null";
} else {
StringBuilder sb = new StringBuilder();
sb.append("[");
for (int i = 0; i < a.length; ++i) {
sb.append(String.valueOf(a[i]));
if (i + 1 != a.length) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
}
private static boolean equal(Object a, Object b) {
return (a == null && b == null) || (a != null && a.equals(b));
}
public static void sort(Object[] array) {
sort(array, new Comparator() {
public int compare(Object a, Object b) {
return ((Comparable) a).compareTo(b);
}
});
}
private final static int SORT_SIZE_THRESHOLD = 16;
public static <T> void sort(T[] array, Comparator<? super T> comparator) {
introSort(array, comparator, 0, array.length, array.length);
insertionSort(array, comparator);
}
private static <T > void introSort(T[] array,
Comparator<? super T> comparator, int begin, int end, int limit)
{
while (end - begin > SORT_SIZE_THRESHOLD) {
if (limit == 0) {
heapSort(array, comparator, begin, end);
return;
}
limit >>= 1;
// median of three
T a = array[begin];
T b = array[begin + (end - begin) / 2 + 1];
T c = array[end - 1];
T median;
if (comparator.compare(a, b) < 0) {
median = comparator.compare(b, c) < 0 ?
b : (comparator.compare(a, c) < 0 ? c : a);
} else {
median = comparator.compare(b, c) > 0 ?
b : (comparator.compare(a, c) > 0 ? c : a);
}
// partition
int pivot, i = begin, j = end;
for (;;) {
while (comparator.compare(array[i], median) < 0) {
++i;
}
--j;
while (comparator.compare(median, array[j]) < 0) {
--j;
}
if (i >= j) {
pivot = i;
break;
}
T swap = array[i];
array[i] = array[j];
array[j] = swap;
++i;
}
introSort(array, comparator, pivot, end, limit);
end = pivot;
}
}
private static <T> void heapSort(T[] array, Comparator<? super T> comparator,
int begin, int end)
{
int count = end - begin;
for (int i = count / 2 - 1; i >= 0; --i) {
siftDown(array, comparator, i, count, begin);
}
for (int i = count - 1; i > 0; --i) {
// swap begin and begin + i
T swap = array[begin + i];
array[begin + i] = array[begin];
array[begin] = swap;
siftDown(array, comparator, 0, i, begin);
}
}
private static <T> void siftDown(T[] array, Comparator<? super T> comparator,
int i, int count, int offset)
{
T value = array[offset + i];
while (i < count / 2) {
int child = 2 * i + 1;
if (child + 1 < count &&
comparator.compare(array[child], array[child + 1]) < 0) {
++child;
}
if (comparator.compare(value, array[child]) >= 0) {
break;
}
array[offset + i] = array[offset + child];
i = child;
}
array[offset + i] = value;
}
private static <T> void insertionSort(T[] array,
Comparator<? super T> comparator)
{
for (int j = 1; j < array.length; ++j) {
T t = array[j];
int i = j - 1;
while (i >= 0 && comparator.compare(array[i], t) > 0) {
array[i + 1] = array[i];
i = i - 1;
}
array[i + 1] = t;
}
}
public static int hashCode(Object[] array) {
if(array == null) {
return 9023;
}
int hc = 823347;
for(Object o : array) {
hc += o != null ? o.hashCode() : 54267;
hc *= 3;
}
return hc;
}
public static boolean equals(Object[] a, Object[] b) {
if(a == b) {
return true;
}
if(a == null || b == null) {
return false;
}
if(a.length != b.length) {
return false;
}
for(int i = 0; i < a.length; i++) {
if(!equal(a[i], b[i])) {
return false;
}
}
return true;
}
public static <T> List<T> asList(final T ... array) {
return new AbstractList<T>() {
public int size() {
return array.length;
}
public void add(int index, T element) {
throw new UnsupportedOperationException();
}
public int indexOf(Object element) {
for (int i = 0; i < array.length; ++i) {
if (equal(element, array[i])) {
return i;
}
}
return -1;
}
public int lastIndexOf(Object element) {
for (int i = array.length - 1; i >= 0; --i) {
if (equal(element, array[i])) {
return i;
}
}
return -1;
}
public T get(int index) {
return array[index];
}
public T set(int index, T value) {
throw new UnsupportedOperationException();
}
public T remove(int index) {
throw new UnsupportedOperationException();
}
public ListIterator<T> listIterator(int index) {
return new Collections.ArrayListIterator(this, index);
}
};
}
public static void fill(int[] array, int value) {
for (int i=0;i<array.length;i++) {
array[i] = value;
}
}
public static void fill(char[] array, char value) {
for (int i=0;i<array.length;i++) {
array[i] = value;
}
}
public static <T> void fill(T[] array, T value) {
for (int i=0;i<array.length;i++) {
array[i] = value;
}
}
}