Java读取文件夹大小的6种方法及代码-原创手记-慕课网

这篇文章介绍了JAVA读取文件夹大小的几种方法实例，有需要的朋友可以参考一下。

(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); 
    } 
}

本文出自：http://developer.51cto.com/art/201503/468128_1.htm