New I/O APIs In Java 7 New Concept

Introduction

In this article we discuss I/O APIs in Java 7.

I/O APIs in Java

Java provides some libraries for input/output operations, in other words reading and writing to files or network sockets. A number of key classes and packages are provided as part of the JDK for dealing with I/O in Java.

Java Packages for dealing with  I/O APIs:

1. java.io
2. java.net
3. java.nio

1. Java.io package

In the beginning Java had only java.io API working with input and output operations on files. This does data stream I/O in Java applications.

It contains classes like:

• FileInputStream
• FileReader
• FileOutputStream
• FileWriter
• BufferedInputStream
• BufferedOutputStream
• ByteArrayOutputStream
• ByteArrayInputStream

2. java.net package

It provides classes to implement network related applications.

It contains several classes:

• ContentHandler
• DatagramPacket
• DatagramSocket
• DatagramSocketImpl
• HttpURLConnection
• InetAddress
• MulticastSocket
• ServerSocket
• Socket
• SocketImpl
• URL
• URLConnection
• URLEncoder
• URLStreamHandler

3. Java.nio package

New I/O, also called nio, is a Java package. It was released with J2SE 1.4 used to extend the features of the java.io package. It provides low-level I/O operations on modern operating systems.

It contains several classes:

• Buffer
• ByteBuffer
• ByteOrder
• CharBuffer
• DoubleBuffer
• FloatBuffer
• IntBuffer
• LongBuffer
• MappedByteBuffer
• ShortBuffer

Limitation

The following are limitations of the current I/O API:

• In the current I/O API there is no guarantee of proper deletion of a file, you must check again and again that the file was deleted.
• Some operations are not scalable on directories and run on the parent thread.
• When some changes happen in a file you need to do polling.

Then came Java 7 that provides a way to handle I/O operations on a file with respect to the underlying file system.

What's New

The following are what's new in the Java 7 I/O APIs:

1. New File System API
2. File Notifications
3. Directory Operations
4. Asynchronous I/0

Reasons

The following are the reasons behind the change in APIs:

     1. In the previous versions the java.io.File class is:

• inconsistent in handling files from various operating systems.
• also inefficient in catching file attributes.
• it has certain limits in accessing functionality from the filesystem.
• when something goes wrong, some of its methods don't throw informative errors.

     2. The work done in the new I/O API provides fast and scalable I/O.

So, Java provides NIO.2, new APIs that provide a better access to the FileSystem.

The new I/O API provides:

• A powerful traversing technique in the file system that helps to perform complex group operations.
• Atomic operations on the file system providing synchronization of processes against file system.
• Custom file systems defined on certain file organization, like archives.
• Updates of specific file and file system objects and their attributes as links, owners and permissions.
• A convenient method to operate on entire file content such as copy, read, edit and move.
• Monitoring file system modifications.

Example

Using JAVA 7 I/O API: we make a program with a .txt file to check the creation date of a file, last access of the file, last update of the file, etc.; see:

import java.text.*;
import java.util.*;
import java.nio.file.*;
import java.nio.file.attribute.*;
public class Nio2Ex
  {
    public static void main(String[] args) throws Exception
      {
        FileSystem flsystem = FileSystems.getDefault();
        Properties pr = System.getProperties();
        String homePathaddress = pr.get("user.home").toString();
        Path homeaddress = flsystem.getPath(homePathaddress);
        System.out.println("File\t\t\tDate Creation \t\tLast File Access\t\tLast File Update");
        try
        ( DirectoryStream<Path> flow = Files.newDirectoryStream(homeaddress, "*.txt"))
          {
            for(Path item : flow)
              {
                BasicFileAttributes atrbs = Files.readAttributes(item, BasicFileAttributes.class);
                Date DateCreate = new Date(atrbs.creationTime().toMillis());
                Date DateAccess = new Date(atrbs.lastAccessTime().toMillis());
                Date DateUpdate = new Date(atrbs.lastModifiedTime().toMillis());
                DateFormat dfrmt = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
                System.out.format("%s\t%s\t%s\t%s%n", item, dfrmt.format(DateCreate), dfrmt.format(DateAccess), dfrmt.format(DateUpdate));
              }
          }
      }
  }

Output