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60. ForkJoinPool





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package com.diguage.truman.concurrent;
import org.junit.jupiter.api.Test;
import java.io.File;
import java.util.LinkedList;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.concurrent.RecursiveTask;
/**
* @author D瓜哥, https://www.diguage.com/
* @since 2020-03-12 10:54
*/
public class ForkJoinPoolTest {
@Test
public void test() {
ForkJoinPool pool = new ForkJoinPool(2);
String homePath = System.getProperty("user.home");
FileCountTask task = new FileCountTask(homePath);
ForkJoinTask<Integer> result = pool.submit(task);
try {
Integer count = result.get();
System.out.println("file count = " + count);
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
pool.shutdown();
while (!pool.isTerminated()) {
}
System.out.println("All thread finish...");
}
public static class FileCountTask extends RecursiveTask<Integer> {
private File file;
public FileCountTask(File file) {
this.file = file;
}
public FileCountTask(String file) {
this.file = new File(file);
}
@Override
protected Integer compute() {
int count = 0;
if (file.isFile()) {
count += 1;
} else {
File[] files = file.listFiles();
if (Objects.isNull(files)) {
files = new File[0];
}
List<FileCountTask> subTasks = new LinkedList<>();
for (File f : files) {
if (f.isDirectory()) {
FileCountTask task = new FileCountTask(f);
subTasks.add(task);
task.fork();
} else {
count += 1;
}
}
for (FileCountTask subTask : subTasks) {
count += subTask.join();
}
}
System.out.printf("%8d %s %n", count, file.getAbsolutePath());
return count;
}
}
}