Java 使用 NIO 方式讀文件

import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.io.File;
import java.io.RandomAccessFile;
import java.io.IOException;

/**

Create a file with holes in it.
/
public class FileHole
{
public static void main (String [] argv)
   throws IOException
{
   // create a temp file, open for writing and get a FileChannel
   File temp = File.createTempFile ("holy", null);
   RandomAccessFile file = new RandomAccessFile (temp, "rw");
   FileChannel channel = file.getChannel();
   // create a working buffer
   ByteBuffer byteBuffer = ByteBuffer.allocateDirect (100);
putData (0, byteBuffer, channel);
   putData (5000000, byteBuffer, channel);
   putData (50000, byteBuffer, channel);
// Size will report the largest position written, but
   // there are two holes in this file.  This file will
   // not consume 5MB on disk (unless the filesystem is
   // extremely brain-damaged).
   System.out.println ("Wrote temp file '" + temp.getPath()

  + "', size=" + channel.size());


channel.close();
   file.close();
}
private static void putData (int position, ByteBuffer buffer,
   FileChannel channel)
   throws IOException
{
   String string = "*<-- location " + position;
buffer.clear();
   buffer.put (string.getBytes ("US-ASCII"));
   buffer.flip();
channel.position (position);
   channel.write (buffer);
}
}</pre>