可以用ExecutorService 这个类，下面是一个用线程池时候下计算文件夹大小的例子，可以参考下

package cq.price;

import java.io.File;

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.Callable;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Future;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.TimeoutException;

public class ConcurrentTotalFileSize {

public static void main(String[] args) throws InterruptedException,

ExecutionException, TimeoutException {

long start = System.nanoTime();

System.out.println("Total Size: "

+ new ConcurrentTotalFileSize()

.getTotalFileSizeOfFilesInDir(new File("F:\资料")));

System.out.println("Time: " + (System.nanoTime() - start)

/ 1.0e9);

}

public long getTotalFileSizeOfFilesInDir(final File file)

throws InterruptedException, ExecutionException, TimeoutException {

if (file.isFile()) {

return file.length();

}

ExecutorService service = Executors.newFixedThreadPool(4);

long total;

try {

total = 0;

List directories = new ArrayList();

directories.add(file);

while (!directories.isEmpty()) {

final List> partialResults = new ArrayList>();

for (final File direcotry : directories) {

partialResults.add(service

.submit(new Callable() {

@Override

public SubDirectoriesAndSize call()

throws Exception {

return getTotalAndSubDirectories(direcotry);

}

}));

}

directories.clear();

for (Future future : partialResults) {

SubDirectoriesAndSize directoriesAndSize = future.get(100,

TimeUnit.SECONDS);

if (directoriesAndSize == null) {

continue;

}

total += directoriesAndSize.size;

directories.addAll(directoriesAndSize.subDirectories);

}

}

} catch (Exception e) {

e.printStackTrace();

throw new RuntimeException(e.getMessage(), e);

} finally {

service.shutdown();

}

return total;

}

public SubDirectoriesAndSize getTotalAndSubDirectories(final File file) {

long total = 0;

List subDirectories = new ArrayList();

if (file.isDirectory()) {

File[] children = file.listFiles();

if (children != null) {

for (File child : children) {

if (child.isFile()) {

total += child.length();

} else {

subDirectories.add(child);

}

}

}

}

return new SubDirectoriesAndSize(total, subDirectories);

}

}

/**

* 记录当初文件夹的下文件的大小以及子文件夹

*

* @author Administrator

*

*/

class SubDirectoriesAndSize {

final public long size;

final public List subDirectories;

public SubDirectoriesAndSize(long size, List subDirectories) {

super();

this.size = size;

this.subDirectories = subDirectories;

};

}