public class Arrays extends Object
In addition to commodity methods, this class contains Swapper-based implementations
of quicksort and of
a stable, in-place mergesort. These
generic sorting methods can be used to sort any kind of list, but they find their natural
usage, for instance, in sorting arrays in parallel.
Arrays| Modifier and Type | Class and Description |
|---|---|
protected static class |
Arrays.ForkJoinGenericQuickSort |
| Modifier and Type | Field and Description |
|---|---|
static int |
MAX_ARRAY_SIZE
This is a safe value used by
ArrayList (as of Java 7) to avoid
throwing OutOfMemoryError on some JVMs. |
| Modifier and Type | Method and Description |
|---|---|
static void |
ensureFromTo(int arrayLength,
int from,
int to)
Ensures that a range given by its first (inclusive) and last (exclusive) elements fits an array of given length.
|
static void |
ensureOffsetLength(int arrayLength,
int offset,
int length)
Ensures that a range given by an offset and a length fits an array of given length.
|
static void |
mergeSort(int from,
int to,
IntComparator c,
Swapper swapper)
Sorts the specified range of elements using the specified swapper and according to the order induced by the specified
comparator using mergesort.
|
static void |
parallelQuickSort(int from,
int to,
IntComparator comp,
Swapper swapper)
Sorts the specified range of elements using the specified swapper and according to the order induced by the specified
comparator using a parallel quicksort.
|
static void |
quickSort(int from,
int to,
IntComparator comp,
Swapper swapper)
Sorts the specified range of elements using the specified swapper and according to the order induced by the specified
comparator using parallel quicksort.
|
protected static void |
swap(Swapper swapper,
int a,
int b,
int n)
Swaps two sequences of elements using a provided swapper.
|
public static final int MAX_ARRAY_SIZE
ArrayList (as of Java 7) to avoid
throwing OutOfMemoryError on some JVMs. We adopt the same value.public static void ensureFromTo(int arrayLength,
int from,
int to)
This method may be used whenever an array range check is needed.
arrayLength - an array length.from - a start index (inclusive).to - an end index (inclusive).IllegalArgumentException - if from is greater than to.ArrayIndexOutOfBoundsException - if from or to are greater than arrayLength or negative.public static void ensureOffsetLength(int arrayLength,
int offset,
int length)
This method may be used whenever an array range check is needed.
arrayLength - an array length.offset - a start index for the fragmentlength - a length (the number of elements in the fragment).IllegalArgumentException - if length is negative.ArrayIndexOutOfBoundsException - if offset is negative or offset+length is greater than arrayLength.public static void mergeSort(int from,
int to,
IntComparator c,
Swapper swapper)
This sort is guaranteed to be stable: equal elements will not be reordered as a result of the sort. The sorting algorithm is an in-place mergesort that is significantly slower than a standard mergesort, as its running time is O(n (log n)2), but it does not allocate additional memory; as a result, it can be used as a generic sorting algorithm.
from - the index of the first element (inclusive) to be sorted.to - the index of the last element (exclusive) to be sorted.c - the comparator to determine the order of the generic data (arguments are positions).swapper - an object that knows how to swap the elements at any two positions.protected static void swap(Swapper swapper, int a, int b, int n)
swapper - the swapper.a - a position in x.b - another position in x.n - the number of elements to exchange starting at a and b.public static void parallelQuickSort(int from,
int to,
IntComparator comp,
Swapper swapper)
The sorting algorithm is a tuned quicksort adapted from Jon L. Bentley and M. Douglas McIlroy, “Engineering a Sort Function”, Software: Practice and Experience, 23(11), pages 1249−1265, 1993.
This implementation uses a ForkJoinPool executor service with Runtime.availableProcessors() parallel threads.
from - the index of the first element (inclusive) to be sorted.to - the index of the last element (exclusive) to be sorted.comp - the comparator to determine the order of the generic data.swapper - an object that knows how to swap the elements at any two positions.public static void quickSort(int from,
int to,
IntComparator comp,
Swapper swapper)
The sorting algorithm is a tuned quicksort adapted from Jon L. Bentley and M. Douglas McIlroy, “Engineering a Sort Function”, Software: Practice and Experience, 23(11), pages 1249−1265, 1993.
This implementation uses a ForkJoinPool executor service with Runtime.availableProcessors() parallel threads.
from - the index of the first element (inclusive) to be sorted.to - the index of the last element (exclusive) to be sorted.comp - the comparator to determine the order of the generic data.swapper - an object that knows how to swap the elements at any two positions.Copyright © 2020. All rights reserved.