如何用Java读取文件夹大小

知识点掌握了，还需要不断练习才能熟练运用。下面golang学习网给大家带来一个文章开发实战，手把手教大家学习《如何用Java读取文件夹大小》，在实现功能的过程中也带大家重新温习相关知识点，温故而知新，回头看看说不定又有不一样的感悟！

(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);     } }

终于介绍完啦！小伙伴们，这篇关于《如何用Java读取文件夹大小》的介绍应该让你收获多多了吧！欢迎大家收藏或分享给更多需要学习的朋友吧~golang学习网公众号也会发布文章相关知识，快来关注吧！