Java by API/java.nio.channels/ReadableByteChannel

ReadableByteChannel: read(ByteBuffer dst)

   <source lang="java">

/*

* Copyright (c) 2004 David Flanagan.  All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book, 
* please visit http://www.davidflanagan.ru/javaexamples3.
*/

//package je3.nio; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.ReadableByteChannel; import java.nio.channels.WritableByteChannel; public class Main {

 public static void main(String[] args) throws IOException {
   // Open file streams and get channels for them.
   ReadableByteChannel in = new FileInputStream(args[0]).getChannel();
   WritableByteChannel out;
   if (args.length > 1)
     out = new FileOutputStream(args[1]).getChannel();
   else
     out = Channels.newChannel(System.out);
   // Do the copy
   copy(in, out);
   // Exception handling and stream-closing code has been omitted.
 }
 // Read all available bytes from one channel and copy them to the other.
 public static void copy(ReadableByteChannel in, WritableByteChannel out) throws IOException {
   // First, we need a buffer to hold blocks of copied bytes.
   ByteBuffer buffer = ByteBuffer.allocateDirect(32 * 1024);
   // Now loop until no more bytes to read and the buffer is empty
   while (in.read(buffer) != -1 || buffer.position() > 0) {
     // The read() call leaves the buffer in "fill mode". To prepare
     // to write bytes from the bufferwe have to put it in "drain mode"
     // by flipping it: setting limit to position and position to zero
     buffer.flip();
     // Now write some or all of the bytes out to the output channel
     out.write(buffer);
     // Compact the buffer by discarding bytes that were written,
     // and shifting any remaining bytes. This method also
     // prepares the buffer for the next call to read() by setting the
     // position to the limit and the limit to the buffer capacity.
     buffer.rupact();
   }
 }

}

 </source>