(一)单线程递归方式

package com.taobao.test;

import java.io.File;

public class TotalFileSizeSequential {

    public static String fileName = "C:\\Documents and Settings\\Administrator\\桌面\\monkeytalk";

    // 递归方式 计算文件的大小

    private long getTotalSizeOfFilesInDir(final File file) {

        if (file.isFile())

            return file.length();

        final File[] children = file.listFiles();

        long total = 0;

        if (children != null)

            for (final File child : children)

                total += getTotalSizeOfFilesInDir(child);

        return total;

    }

    public static void main(final String[] args) {

        final long start = System.nanoTime();

        final long total = new TotalFileSizeSequential()

                .getTotalSizeOfFilesInDir(new File(fileName));

        final long end = System.nanoTime();

        System.out.println("Total Size: " + total);

        System.out.println("Time taken: " + (end - start) / 1.0e9);

    }

}

（二）使用Executors.newFixedThreadPool和callable 多线程实现

package com.taobao.test;

import java.io.File;

import java.util.ArrayList;

import java.util.Collections;

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 final String fileName = "C:\\Documents and Settings\\Administrator\\桌面\\monkeytalk";

    class SubDirectoriesAndSize {

        final public long size;

        final public List<File> subDirectories;

        public SubDirectoriesAndSize(final long totalSize,

                final List<File> theSubDirs) {

            size = totalSize;

            subDirectories = Collections.unmodifiableList(theSubDirs);

        }

    }

    private SubDirectoriesAndSize getTotalAndSubDirs(final File file) {

        long total = 0;

        final List<File> subDirectories = new ArrayList<File>();

        if (file.isDirectory()) {

            final File[] children = file.listFiles();

            if (children != null)

                for (final File child : children) {

                    if (child.isFile())

                        total += child.length();

                    else

                        subDirectories.add(child);

                }

        }

        return new SubDirectoriesAndSize(total, subDirectories);

    }

    private long getTotalSizeOfFilesInDir(final File file)

            throws InterruptedException, ExecutionException, TimeoutException {

        final ExecutorService service = Executors.newFixedThreadPool(100);

        try {

            long total = 0;

            final List<File> directories = new ArrayList<File>();

            directories.add(file);

            while (!directories.isEmpty()) {

                final List<Future<SubDirectoriesAndSize>> partialResults = new ArrayList<Future<SubDirectoriesAndSize>>();

                for (final File directory : directories) {

                    partialResults.add(service

                            .submit(new Callable<SubDirectoriesAndSize>() {

                                public SubDirectoriesAndSize call() {

                                    return getTotalAndSubDirs(directory);

                                }

                            }));

                }

                directories.clear();

                for (final Future<SubDirectoriesAndSize> partialResultFuture : partialResults) {

                    final SubDirectoriesAndSize subDirectoriesAndSize = partialResultFuture

                            .get(100, TimeUnit.SECONDS);

                    directories.addAll(subDirectoriesAndSize.subDirectories);

                    total += subDirectoriesAndSize.size;

                }

            }

            return total;

        } finally {

            service.shutdown();

        }

    }

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

            ExecutionException, TimeoutException {

        final long start = System.nanoTime();

        final long total = new ConcurrentTotalFileSize()

                .getTotalSizeOfFilesInDir(new File(fileName));

        final long end = System.nanoTime();

        System.out.println("Total Size: " + total);

        System.out.println("Time taken: " + (end - start) / 1.0e9);

    }

}

（三）使用Executors.newFixedThreadPool和callable 多线程的另外一种实现

package com.taobao.test;

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 NaivelyConcurrentTotalFileSize {

    public static String fileName = "C:\\Documents and Settings\\Administrator\\桌面\\monkeytalk";

    private long getTotalSizeOfFilesInDir(final ExecutorService service,

            final File file) throws InterruptedException, ExecutionException,

            TimeoutException {

        if (file.isFile())

            return file.length();

        long total = 0;

        final File[] children = file.listFiles();

        if (children != null) {

            final List<Future<Long>> partialTotalFutures = new ArrayList<Future<Long>>();

            for (final File child : children) {

                partialTotalFutures.add(service.submit(new Callable<Long>() {

                    public Long call() throws InterruptedException,

                            ExecutionException, TimeoutException {

                        return getTotalSizeOfFilesInDir(service, child);

                    }

                }));

            }

            for (final Future<Long> partialTotalFuture : partialTotalFutures)

                total += partialTotalFuture.get(100, TimeUnit.SECONDS);

        }

        return total;

    }

    private long getTotalSizeOfFile(final String fileName)

            throws InterruptedException, ExecutionException, TimeoutException {

        final ExecutorService service = Executors.newFixedThreadPool(100);

        try {

            return getTotalSizeOfFilesInDir(service, new File(fileName));

        } finally {

            service.shutdown();

        }

    }

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

            ExecutionException, TimeoutException {

        final long start = System.nanoTime();

        final long total = new NaivelyConcurrentTotalFileSize()

                .getTotalSizeOfFile(fileName);

        final long end = System.nanoTime();

        System.out.println("Total Size: " + total);

        System.out.println("Time taken: " + (end - start) / 1.0e9);

    }

}

（四）使用CountDownLatch和AtomicLong实现多线程下的并发控制

package com.taobao.test;

import java.io.File;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicLong;

public class ConcurrentTotalFileSizeWLatch {

    private ExecutorService service;

    final private AtomicLong pendingFileVisits = new AtomicLong();

    final private AtomicLong totalSize = new AtomicLong();

    final private CountDownLatch latch = new CountDownLatch(1);

    public static String fileName = "C:\\Documents and Settings\\Administrator\\桌面\\monkeytalk";

    private void updateTotalSizeOfFilesInDir(final File file) {

        long fileSize = 0;

        if (file.isFile())

            fileSize = file.length();

        else {

            final File[] children = file.listFiles();

            if (children != null) {

                for (final File child : children) {

                    if (child.isFile())

                        fileSize += child.length();

                    else {

                        pendingFileVisits.incrementAndGet();

                        service.execute(new Runnable() {

                            public void run() {

                                updateTotalSizeOfFilesInDir(child);

                            }

                        });

                    }

                }

            }

        }

        totalSize.addAndGet(fileSize);

        if (pendingFileVisits.decrementAndGet() == 0)

            latch.countDown();

    }

    private long getTotalSizeOfFile(final String fileName)

            throws InterruptedException {

        service = Executors.newFixedThreadPool(100);

        pendingFileVisits.incrementAndGet();

        try {

            updateTotalSizeOfFilesInDir(new File(fileName));

            latch.await(100, TimeUnit.SECONDS);

            return totalSize.longValue();

        } finally {

            service.shutdown();

        }

    }

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

        final long start = System.nanoTime();

        final long total = new ConcurrentTotalFileSizeWLatch()

                .getTotalSizeOfFile(fileName);

        final long end = System.nanoTime();

        System.out.println("Total Size: " + total);

        System.out.println("Time taken: " + (end - start) / 1.0e9);

    }

}

（五）使用BlockingQueue和AtomicLong的实现

package com.taobao.test;

import java.io.File;

import java.util.concurrent.ArrayBlockingQueue;

import java.util.concurrent.BlockingQueue;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicLong;

public class ConcurrentTotalFileSizeWQueue {

    public static String fileName = "C:\\Documents and Settings\\Administrator\\桌面\\monkeytalk";

    private ExecutorService service;

    final private BlockingQueue<Long> fileSizes = new ArrayBlockingQueue<Long>(

            500);

    final AtomicLong pendingFileVisits = new AtomicLong();

    private void startExploreDir(final File file) {

        pendingFileVisits.incrementAndGet();

        service.execute(new Runnable() {

            public void run() {

                exploreDir(file);

            }

        });

    }

    private void exploreDir(final File file) {

        long fileSize = 0;

        if (file.isFile())

            fileSize = file.length();

        else {

            final File[] children = file.listFiles();

            if (children != null)

                for (final File child : children) {

                    if (child.isFile())

                        fileSize += child.length();

                    else {

                        startExploreDir(child);

                    }

                }

        }

        try {

            fileSizes.put(fileSize);

        } catch (Exception ex) {

            throw new RuntimeException(ex);

        }

        pendingFileVisits.decrementAndGet();

    }

    private long getTotalSizeOfFile(final String fileName)

            throws InterruptedException {

        service = Executors.newFixedThreadPool(100);

        try {

            startExploreDir(new File(fileName));

            long totalSize = 0;

            while (pendingFileVisits.get() > 0 || fileSizes.size() > 0) {

                final Long size = fileSizes.poll(10, TimeUnit.SECONDS);

                totalSize += size;

            }

            return totalSize;

        } finally {

            service.shutdown();

        }

    }

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

        final long start = System.nanoTime();

        final long total = new ConcurrentTotalFileSizeWQueue()

                .getTotalSizeOfFile(fileName);

        final long end = System.nanoTime();

        System.out.println("Total Size: " + total);

        System.out.println("Time taken: " + (end - start) / 1.0e9);

    }

}

(六)使用jdk7的ForkJoin来实现

package com.taobao.test;

import java.io.File;

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.ForkJoinPool;

import java.util.concurrent.ForkJoinTask;

import java.util.concurrent.RecursiveTask;

public class FileSize {

    private final static ForkJoinPool forkJoinPool = new ForkJoinPool();

    public static String fileName = "C:\\Documents and Settings\\Administrator\\桌面\\monkeytalk";

    private static class FileSizeFinder extends RecursiveTask<Long> {

        final File file;

        public FileSizeFinder(final File theFile) {

            file = theFile;

        }

        @Override

        public Long compute() {

            long size = 0;

            if (file.isFile()) {

                size = file.length();

            } else {

                final File[] children = file.listFiles();

                if (children != null) {

                    List<ForkJoinTask<Long>> tasks = new ArrayList<ForkJoinTask<Long>>();

                    for (final File child : children) {

                        if (child.isFile()) {

                            size += child.length();

                        } else {

                            tasks.add(new FileSizeFinder(child));

                        }

                    }

                    for (final ForkJoinTask<Long> task : invokeAll(tasks)) {

                        size += task.join();

                    }

                }

            }

            return size;

        }

    }

    public static void main(final String[] args) {

        final long start = System.nanoTime();

        final long total = forkJoinPool.invoke(new FileSizeFinder(new File("/home")));

        final long end = System.nanoTime();

        System.out.println("Total Size: " + total);

        System.out.println("Time taken: " + (end - start) / 1.0e9);

    }

}

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