对映射文件的部分加锁

package io;

//: io/LockingMappedFiles.java
// Locking portions of a mapped file.
// {RunByHand}
import java.nio.*;
import java.nio.channels.*;
import java.io.*;

public class LockingMappedFiles {
	static final int LENGTH = 0xA00000; // 10 MB
	static FileChannel fc;

	public static void main(String[] args) throws IOException {
		fc = new RandomAccessFile("test.dat", "rw").getChannel();
		MappedByteBuffer mbb = fc
				.map(FileChannel.MapMode.READ_WRITE, 0, LENGTH);
		for (int i = 0; i < LENGTH; i++) {
			mbb.put((byte) 'x');
		}
		new LockAndModify(mbb, 0, 0 + LENGTH/3);
		new LockAndModify(mbb, LENGTH/2, LENGTH/2+LENGTH/4);
		
	}

	public static class LockAndModify extends Thread {

		int start;
		int end;
		ByteBuffer bbf;
		public LockAndModify(ByteBuffer mbb, int start, int end) {
			this.start = start;
			this.end = end;
			mbb.limit(end);
			mbb.position(start);
			bbf = mbb.slice();
			start();
		}

		@Override
		public void run() {
			try {
				FileLock fl = fc.lock(start, end, false);
				System.out.println("Locked " + start + "to " + end);
				while(bbf.position() < bbf.limit()-1){
					//put方法会增加position的值
					bbf.put((byte)(bbf.get()+2));
				}
				fl.release();
				System.out.println("release " + start + "to " + end);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			
		}
	}

} // /:~