在oschina上看到一篇排序速度测试的(http://my.oschina.net/nox/blog/489993?fromerr=W8001KYQ),但没有测试stream的速度.故增加该测试.
三种排序方式:
1.Collections.sort;
2.forkjoin;
3.stream sort.
上代码:
package sort;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;
import java.util.stream.Collectors;
public class GenerateSample {
public static void main(String[] args) {
writeFile();
long t1 = System.currentTimeMillis();
sort();
long t2 = System.currentTimeMillis();
System.out.println("sort total time=" + (t2-t1));
forkJoin();
long t3 = System.currentTimeMillis();
System.out.println("forkjoin total time=" + (t3-t2));
stream();
long t4 = System.currentTimeMillis();
System.out.println("stream total time=" + (t4-t3));
}
public static void writeFile() {
File f = new File("/home/novelbio/tmp/sample.txt");
FileWriter writer;
try {
writer = new FileWriter(f, false);
Random random1 = new Random(10);
for (int i = 0; i < 10000000; i++) {
writer.write(String.valueOf(random1.nextInt(20000)));
writer.write("\r\n");
}
writer.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
public static void sort() {
File f = new File("/home/novelbio/tmp/sample.txt");
List<Integer> arrayList = new ArrayList<>();
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(f));
String str = null;
while ((str = reader.readLine()) != null) {
arrayList.add(Integer.valueOf(str));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
long startTime = System.currentTimeMillis();
Collections.sort(arrayList);
long endTime = System.currentTimeMillis();
System.out.println("基本sort排序所花时间:" + (endTime - startTime) + "ms");
File f2 = new File("/home/novelbio/tmp/original_sorted.txt");
FileWriter writer2;
try {
writer2 = new FileWriter(f2, false);
for (int i = 0; i < arrayList.size(); i++) {
writer2.write(String.valueOf(arrayList.get(i)));
writer2.write("\r\n");
}
writer2.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
public static void forkJoin() {
File f = new File("/home/novelbio/tmp/sample.txt");
List<Integer> arrayList = new ArrayList<>();
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(f));
String str = null;
while ((str = reader.readLine()) != null) {
arrayList.add(Integer.valueOf(str));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
long longArray[] = new long[arrayList.size()];
for (int i = 0; i < arrayList.size(); i++) {
longArray[i] = Long.parseLong(arrayList.get(i).toString());
}
ForkJoinPool pool = new ForkJoinPool();
FastSort fastSort = new FastSort(longArray);
long startTime = System.currentTimeMillis();
pool.execute(fastSort);
while (!fastSort.isDone()) {
}
long endTime = System.currentTimeMillis();
System.out.println("fockJoin排序所花时间:" + (endTime - startTime) + "ms");
File f2 = new File("/home/novelbio/tmp/fockJoinSorted.txt");
FileWriter writer2;
try {
writer2 = new FileWriter(f2, false);
for (int i = 0; i < longArray.length; i++) {
writer2.write(String.valueOf(longArray[i]));
writer2.write("\r\n");
}
writer2.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
public static void stream() {
File f = new File("/home/novelbio/tmp/sample.txt");
List<Integer> arrayList = new ArrayList<>();
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(f));
String str = null;
while ((str = reader.readLine()) != null) {
arrayList.add(Integer.valueOf(str));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
long startTime = System.currentTimeMillis();
ArrayList<Integer> newlist = (ArrayList) arrayList.stream().sorted((p1, p2) -> (p1 - p2)).collect(Collectors.toList());
long endTime = System.currentTimeMillis();
System.out.println("streamSorted排序所花时间:" + (endTime - startTime) + "ms");
File f2 = new File("/home/novelbio/tmp/streamSorted.txt");
FileWriter writer2;
try {
writer2 = new FileWriter(f2, false);
for (Integer i : newlist) {
writer2.write(String.valueOf(i));
writer2.write("\r\n");
}
writer2.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
}
class FastSort extends RecursiveAction {
private static final long serialVersionUID = 1L;
final long[] array;
final int lo;
final int hi;
private int THRESHOLD = 30;
public FastSort(long[] array) {
this.array = array;
this.lo = 0;
this.hi = array.length - 1;
}
public FastSort(long[] array, int lo, int hi) {
this.array = array;
this.lo = lo;
this.hi = hi;
}
protected void compute() {
if (hi - lo < THRESHOLD)
sequentiallySort(array, lo, hi);
else {
int pivot = partition(array, lo, hi);
FastSort left = new FastSort(array, lo, pivot - 1);
FastSort right = new FastSort(array, pivot + 1, hi);
invokeAll(left, right);
}
}
private int partition(long[] array, int lo, int hi) {
long x = array[hi];
int i = lo - 1;
for (int j = lo; j < hi; j++) {
if (array[j] <= x) {
i++;
swap(array, i, j);
}
}
swap(array, i + 1, hi);
return i + 1;
}
private void swap(long[] array, int i, int j) {
if (i != j) {
long temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
private void sequentiallySort(long[] array, int lo, int hi) {
Arrays.sort(array, lo, hi + 1);
}
}
测试结果如下(每人机器配置不同,花费时间会有不同.):
基本sort排序所花时间:3627ms sort total time=8176 fockJoin排序所花时间:1345ms forkjoin total time=5846 streamSorted排序所花时间:2581ms stream total time=5566
基本结论:
基本sort(3627ms)>streamSorted(2581ms)>fockJoin(1345ms)