避免的Java 8 Files.walk（..）的（java.nio.file.AccessDeniedException）終止原因

Question

Description

我使用的Java 8Files.walk(..)計算包含在文件夾內的文件.mp3和它裏面的所有文件夾。換句話說，我正在訪問文件樹的所有級別。

當我得到java.nio.file.AccessDeniedExceptionStream關閉，我不希望這種行爲。我需要它忽略或打印異常並繼續計數文件。下面是我使用的代碼:)：

  /** 
      * Count files in a directory (including files in all sub 
      * directories) 
      * 
      * @param directory 
      *  the directory to start in 
      * @return the total number of files 
      */ 
      public int countFiles(File dir) { 
       if (dir.exists()) 
        try (Stream<Path> paths = Files.walk(Paths.get(dir.getPath()), FileVisitOption.FOLLOW_LINKS)) { 
         return (int) paths.filter(path -> { 

          // i am using something different here but i changed 
          // it just for the purpose of StackOverFlow question         
          return path.toString().contains(".mp3"); 

         }).count(); 
        } catch (IOException ex) { 
         //Main.logger.log(Level.WARNING, "", ex); 
         ex.printStackTrace(); 
        } 

       return 0; 
      } 

StackTrace of error:

java.io.UncheckedIOException: java.nio.file.AccessDeniedException: C:\$Recycle.B 
in\S-1-5-18 
    at java.nio.file.FileTreeIterator.fetchNextIfNeeded(FileTreeIterator.java:88) 
    at java.nio.file.FileTreeIterator.hasNext(FileTreeIterator.java:104) 
    at java.util.Iterator.forEachRemaining(Iterator.java:115) 
    at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.jav 
a:1801) 
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) 
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) 
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) 
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) 
    at java.util.stream.LongPipeline.reduce(LongPipeline.java:438) 
    at java.util.stream.LongPipeline.sum(LongPipeline.java:396) 
    at java.util.stream.ReferencePipeline.count(ReferencePipeline.java:526) 
    at smartcontroller.SmartController$InputService$1.countFiles(SmartController.ja 
va:2092) 
... 

Similar question , though not the same i need a Stream to be returned .

Working around access denied in a FileWalking Tree in Java7。

---

Answer 1

回答

這裏是一個臨時解決方案，其可被改進，以使用Java 8流和lambda表達式。

int[] count = {0}; 
try { 
    Files.walkFileTree(Paths.get(dir.getPath()), new HashSet<FileVisitOption>(Arrays.asList(FileVisitOption.FOLLOW_LINKS)), 
      Integer.MAX_VALUE, new SimpleFileVisitor<Path>() { 
       @Override 
       public FileVisitResult visitFile(Path file , BasicFileAttributes attrs) throws IOException { 
        System.out.printf("Visiting file %s\n", file); 
        ++count[0]; 

        return FileVisitResult.CONTINUE; 
       } 

       @Override 
       public FileVisitResult visitFileFailed(Path file , IOException e) throws IOException { 
        System.err.printf("Visiting failed for %s\n", file); 

        return FileVisitResult.SKIP_SUBTREE; 
       } 

       @Override 
       public FileVisitResult preVisitDirectory(Path dir , BasicFileAttributes attrs) throws IOException { 
        System.out.printf("About to visit directory %s\n", dir); 
        return FileVisitResult.CONTINUE; 
       } 
      }); 
} catch (IOException e) { 
    // TODO Auto-generated catch block 
    e.printStackTrace(); 
}