Java 8在Java.util.Arrays类中引入了一个称为parallelSort()的新方法。它使用数组元素的并行排序
parallelSort()算法
1. The array is divided into sub-arrays and that
sub-arrays is again divided into their sub-arrays,
until the minimum level of detail in a set of array.
2. Arrays are sorted individually by multiple thread.
3. The parallel sort uses Fork/Join Concept for sorting.
4. Sorted sub-arrays are then merged.
句法 :
- 为了按升序对数据进行排序:
public static void parallelSort(Object obj[])
- 用于按指定顺序对指定范围内的数据进行升序排序:
public static void parallelSort(Object obj[], int from, int to)
优势 :
parallelSort()方法使用MultiThreading的概念,与常规排序方法相比,它使排序更快。
例子
下面是说明Arrays.parallelSort()用法的程序:
程序1:演示并行排序的使用
// Java program to demonstrate
// Arrays.parallelSort() method
import java.util.Arrays;
public class ParallelSort {
public static void main(String[] args)
{
// Creating an array
int numbers[] = { 9, 8, 7, 6, 3, 1 };
// Printing unsorted Array
System.out.print("Unsorted Array: ");
// Iterating the Elements using stream
Arrays.stream(numbers)
.forEach(n -> System.out.print(n + " "));
System.out.println();
// Using Arrays.parallelSort()
Arrays.parallelSort(numbers);
// Printing sorted Array
System.out.print("Sorted Array: ");
// Iterating the Elements using stream
Arrays.stream(numbers)
.forEach(n -> System.out.print(n + " "));
}
}
输出:
Unsorted Array: 9 8 7 6 3 1
Sorted Array: 1 3 6 7 8 9
时间复杂度为O(nlogn)
程序2:演示并行排序wrt系列排序(普通排序)的用法
// Java program to demonstrate impact
// of Parallel Sort vs Serial Sort
import java.util.Arrays;
import java.util.Random;
public class ParallelSort {
public static void main(String[] args)
{
// Creating an array
int numbers[] = new int[100];
// Iterating Loop till i = 1000
// with interval of 10
for (int i = 0; i < 1000; i += 10) {
System.out.println("\nFor iteration number: "
+ (i / 10 + 1));
// Random Int Array Generation
Random rand = new Random();
for (int j = 0; j < 100; j++) {
numbers[j] = rand.nextInt();
}
// Start and End Time of Arrays.sort()
long startTime = System.nanoTime();
// Performing Serial Sort
Arrays.sort(numbers);
long endTime = System.nanoTime();
// Printing result of Serial Sort
System.out.println("Start and End Time in Serial (in ns): "
+ startTime + ":" + endTime);
System.out.println("Time taken by Serial Sort(in ns): "
+ (endTime - startTime));
// Start and End Time of Arrays.parallelSort()
startTime = System.nanoTime();
// Performing Parallel Sort
Arrays.parallelSort(numbers);
endTime = System.nanoTime();
// Printing result of Parallel Sort
System.out.println("Start and End Time in parallel (in ns): "
+ startTime + ":" + endTime);
System.out.println("Time taken by Parallel Sort(in ns): "
+ (endTime - startTime));
System.out.println();
}
}
}
输出:
For iteration number: 1
Start and End Time in Serial (in ns): 3951000637977:3951000870361
Time taken by Serial Sort(in ns): 232384
Start and End Time in parallel (in ns): 3951000960823:3951000971044
Time taken by Parallel Sort(in ns): 10221
For iteration number: 2
Start and End Time in Serial (in ns): 3951001142284:3951001201757
Time taken by Serial Sort(in ns): 59473
Start and End Time in parallel (in ns): 3951001256643:3951001264039
Time taken by Parallel Sort(in ns): 7396
.
.
.
For iteration number: 99
Start and End Time in Serial (in ns): 3951050723541:3951050731520
Time taken by Serial Sort(in ns): 7979
Start and End Time in parallel (in ns): 3951050754238:3951050756130
Time taken by Parallel Sort(in ns): 1892
For iteration number: 100
Start and End Time in Serial (in ns): 3951050798392:3951050804741
Time taken by Serial Sort(in ns): 6349
Start and End Time in parallel (in ns): 3951050828544:3951050830582
Time taken by Parallel Sort(in ns): 2038
注意:将打印不同的时间间隔,但是将在正常排序之前进行并行排序。
环境: 2.6 GHz Intel Core i7, Java版本8