A channel is an open connection between a data source and a Java program.
The Channel interface in the java.nio.channels package represents channels in Java.
To obtain a channel, create an object of InputStream and OutputStream.
Utility Channels class converts streams into channels and vice versa.
The following code gets a ReadableByteChannel from input stream object
// Get a ReadableByteChannel from an InputStream ReadableByteChannel rbc = Channels.newChannel(myInputStream);
Obtain the underlying InputStream object
// Get the InputStream of the ReadableByteChannel InputStream myInputStream = Channels.newInputStream(rbc);
FileInputStream and FileOutputStream classes have a new method called getChannel() to return a FileChannel object.
A FileChannel is used to read and write data to a file.
The FileChannel object obtained from a FileInputStream is opened in a read-only mode.
The FileChannel object obtained from a FileOutputStream object is opened in a write-only mode.
The FileChannel from a RandomAccessFile is opened in a read-only, write-only, or read-write mode, depending on the way you create that RandomAccessFile object.
The following code obtains FileChannel objects for different kinds of file streams:
FileInputStream fis = new FileInputStream("Main.java"); FileChannel fcReadOnly = fis.getChannel(); // A read-only channel FileOutputStream fos = new FileOutputStream("Main.java"); FileChannel fcWriteOnly = fos.getChannel(); // A write-only channel // Open file in a read-only mode RandomAccessFile raf1 = new RandomAccessFile("Main.java", "r"); FileChannel rafReadOnly = raf1.getChannel(); // A read-only channel // Open file in a read-write mode RandomAccessFile raf2 = new RandomAccessFile("Main.java", "rw"); FileChannel rafReadWrite = raf2.getChannel(); // A read-write channel
You can get a FileChannel using the FileChannel.open() static method.