This is my slides from the JavaZone conference. I presented NIO.2 and here are the slides.

1. NIO.2: The I/O API For Future Masoud Kalali [email_address] Twitter: @MasoudKalali http://kalali.me

3. Java I/O history from Java 1.0 to Java 7 I/O in Java 1.1 NIO (JSR-51) in JDK 1.4 NIO.2 (JSR-203) in Java 7

7. How the NIO.2 works FileSystem fs = FileSystems.getDefault(); Path p = fs.getPath("/home/masoud/simple.txt"); try { p.deleteIfExists(); } catch (IOException ex) { //handle it } Basically everything start with FileSystems and FileSystem object

10. Walking The File System Tree • Files.walkFileTree * Walks a file tree from a given starting path down to the given depth * Invoke FileVisitor methods for each file/directory public class SimpleVisitor { public static void main(String args[]) { FileSystem fs = FileSystems.getDefault(); Path p = fs.getPath(&quot;/home/masoud/&quot;); MyVisit v = new MyVisit(); Files.walkFileTree(p, EnumSet.allOf(FileVisitOption.class), 2, v); } } class MyVisit extends SimpleFileVisitor<Path> { @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) { System.out.println(file.getName()); return super.visitFile(file, attrs); } } PreVisitDirectory PreVisitDirectoryFailed VisitFile VisitFileFailed postVisitDirectory

12. File attributes and metadata: basic attributes BasicFileAttributes: Common to all FS and contains basic attributes. Creation Time Last Access Time Modification Time Size File Type: isDirectory, IsFile, IsSymbolicLink, IsOther File Key FileSystem fs = FileSystems.getDefault(); Path p = fs.getPath(&quot;/home/masoud/simple&quot;); BasicFileAttributeView bav= p.getFileAttributeView(BasicFileAttributeView.class, LinkOption.NOFOLLOW_LINKS); BasicFileAttributes ba =bav.readAttributes(); System.out.println(p.toString() + &quot; last access: &quot; + ba.lastAccessTime()); System.out.println(p.toString() + &quot; last modified: &quot; + ba.lastModifiedTime());

13. File attributes and metadata: Platform specific Attributes PosixFileAttributeView Extends BasicFileAttributeView, contain Posix specific attributes. FileSystem fs = FileSystems.getDefault(); Path p = fs.getPath(&quot;/home/masoud/photo.png&quot;); Set<String> supportedViews = fs.supportedFileAttributeViews(); if (supportedViews.contains(&quot;unix&quot;)) { PosixFileAttributes pat = Attributes.readPosixFileAttributes(p, LinkOption.NOFOLLOW_LINKS); System.out.println(pat.group().getName()); System.out.println(pat.owner(). } All Basic attributes Retrieving group Retrieving owner Retrieving permission basic unix dos acl owner user etc.

16. //Setting permissions Set<PosixFilePermission> st = PosixFilePermissions.fromString(&quot;rwxrwxrwx&quot;); Attributes.setPosixFilePermissions(p, st2); //Setting the owner username, we should find the user prior to using Attributes utility class UserPrincipal up = s.getUserPrincipalLookupService().lookupPrincipalByName(&quot;masoud&quot;); Attributes.setOwner(p, up); //Another way to set the owner name. FileOwnerAttributeView fo = p.getFileAttributeView(FileOwnerAttributeView.class, LinkOption.NOFOLLOW_LINKS); fo.setOwner(up); FileOwnerView: Deal with file owner attribute Attributes: To write attributes, PosixFileAttributes includes permissions as well. File attributes and metadata: Managing POSIX files permissions

17. FileStore features The FileStore : Represent the file system underlying storage devices, pools, partitions, and so on. FileSystem fs = FileSystems.getFileSystem(new URI(&quot;File:///&quot;)); Path p = fs.getPath(&quot;/home/masoud&quot;); FileStore fstore = p.getFileStore(); FileStoreSpaceAttributes attrs = Attributes.readFileStoreSpaceAttributes(fstore); long total = attrs.totalSpace() / (1024*1024); long used = (attrs.totalSpace() - attrs.unallocatedSpace()) / (1024*1024); long avail = attrs.usableSpace() /(1024*1024); System.out.println(&quot; device size(MB) used(MB) available(MB) &quot;); System.out.format(&quot;%-20s %12d %12d %12d%n&quot;, fstore, total, used, avail); We can use FileSystem.getFileStores() to get all underlying file stores.

20. Change notification: Sample Code FileSystem fs = FileSystems.getDefault(); WatchService ws = fs.newWatchService(); Path path = fs.getPath(&quot;/home/masoud/Pictures&quot;); path.register(ws, StandardWatchEventKind.ENTRY_CREATE, StandardWatchEventKind.ENTRY_DELETE); WatchKey key = ws.take(); List<WatchEvent<?>> events = key.pollEvents(); for (WatchEvent object : events) { if (object.kind() == StandardWatchEventKind.ENTRY_DELETE) { System.out.println(&quot;Delete: &quot; + path.toRealPath(true)+&quot;/&quot;+ object.context().toString()); } if (object.kind() == StandardWatchEventKind.ENTRY_CREATE) { System.out.println(&quot;Created: &quot; + path.toRealPath(true)+&quot;/&quot;+ object.context().toString()); } }

22. Blocking, Non-Blocking and Asynchronous I/O Prior to Java SE 1.4 : Everything was blocking and and use of threads was inevitable. ( which causes scalability issues and performance overhead) Java SE 1.4 : Brings the JSR-51 or NIO with non-blocking IO; Introduction of channels and selectors. Non-Blocking not Asynchronous. Java SE 7 : Addition of asynchronous IO to the pack; included inside java.nio.channels

24. Sample code for Asynchronous I/O: Using Future FileSystem fs = FileSystems.getDefault(); Path path = fs.getPath (&quot;/home/masoud/a.png&quot;); AsynchronousFileChannel ch = AsynchronousFileChannel.open (path); ByteBuffer buf = ByteBuffer.allocate (2048); Future<Integer> result = ch.read (buf,0); while (!result.isDone ()) { System.out.println (&quot;Doing something else&quot;); Thread.sleep (500); } System.out.println (&quot;Bytes we read: &quot;+result.get ()); ch.close (); The Future object allows us to check on the status of the asynchronous job when we want to get back at it.

25. Sample code for Asynchronous I/O: Using Callback Path path = Paths.get(&quot;/home/masoud/series.txt&quot;); AsynchronousFileChannel ch = AsynchronousFileChannel.open(path); final ByteBuffer buf = ByteBuffer.allocate(2048); ch.read(buf, 0, buf, new SimpleHandler()); class SimpleHandler implements CompletionHandler<Integer, ByteBuffer> { public void completed(Integer result, ByteBuffer attachment) { System.out.println(new String(attachment.array())); } public void failed(Throwable th, ByteBuffer attachment) { System.out.println(th.toString()); } } interface CompletionHandler<V,A> Attachment is something to carry a context object into the handler. Value number of bytes we read or write. read(ByteBuffer dst, long position, A attachment, CompletionHandler<Integer,? super A> handler) interface CompletionHandler<V,A> Attachment is something to carry a context object into the handler. Value number of bytes we read or write.

27. Other JSR 203 features The java.io.File.getPath() method File type MIME detection using Files.probeContentType

28. More Information OpenJDK New I/O Project – http://openjdk.java.net/projects/nio Questions?

29. Thank you Thank you for joining this session Masoud Kalali http://kalali.me Twitter: @MasoudKalali [email_address]