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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
     
       subDirectories;        public SubDirectoriesAndSize(final long totalSize,                final List
      
        theSubDirs) {            size = totalSize;            subDirectories = Collections.unmodifiableList(theSubDirs);        }    }    private SubDirectoriesAndSize getTotalAndSubDirs(final File file) {        long total = 0;        final List
       
         subDirectories = new ArrayList
        
         ();        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
         
           directories = new ArrayList
          
           (); directories.add(file); while (!directories.isEmpty()) { final List
           
            
             > partialResults = new ArrayList
             
              
               >(); for (final File directory : directories) { partialResults.add(service .submit(new Callable
               
                () { public SubDirectoriesAndSize call() { return getTotalAndSubDirs(directory); } })); } directories.clear(); for (final Future
                
                  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
     
      
       > partialTotalFutures = new ArrayList
       
        
         >();            for (final File child : children) {                partialTotalFutures.add(service.submit(new Callable
         
          () {                    public Long call() throws InterruptedException,                            ExecutionException, TimeoutException {                        return getTotalSizeOfFilesInDir(service, child);                    }                }));            }            for (final Future
          
            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
     
       fileSizes = new ArrayBlockingQueue
      
       (            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
     
       {
              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
      
       
        > tasks = new ArrayList
        
         
          >();                    for (final File child : children) {                        if (child.isFile()) {                            size += child.length();                        } else {                            tasks.add(new FileSizeFinder(child));                        }                    }                    for (final ForkJoinTask
          
            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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学习过程中遇到什么问题或者想获取学习资源的话，欢迎加入Java学习交流群，群号码：279558494 我们一起学Java！

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