java 内存映射文件 大文件操作

/**
 * 内存映射文件
 * @author Administrator
 *
 */
public class LargeMappedFiles {
	private static int length = 0x8FFFFFF;

	public static void main(String args[]) {
		try {
			MappedByteBuffer out = new RandomAccessFile(new File("D:\\Niotest.txt"), "rw")
					.getChannel()
					.map(FileChannel.MapMode.READ_WRITE, 0, length);
			for(int i = 0; i < length;i++){
				out.put((byte)'x');
			}
			System.out.println("Finished writing");
			for(int i = length/2;i<length/2+6;i++){
				System.out.println((char)out.get(i));
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

  

   内存映射文件上锁和部分内容上锁

  

  

/**
 * 文件映射 针对大文件
 * 大文件部分文件加锁
 * @author Administrator
 *
 */
public class LockingMappedFiles {
	static FileChannel fc;
	static final int LENGTH = 0x8FFFFFF;
	
	public static void main(String args[]){
		try {
			fc = new RandomAccessFile("D:\\test.dat","rw").getChannel();
			MappedByteBuffer out = fc.map(FileChannel.MapMode.READ_WRITE, 0, LENGTH);
			for(int i = 0 ;i < LENGTH ;i++){
				out.put((byte)'X');
			}
			new LockAndModify(out,0,0+LENGTH/3);
			new LockAndModify(out,LENGTH/2,LENGTH/2+LENGTH/4);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	private static class LockAndModify extends Thread{
		private ByteBuffer buff;
		private int start,end;
		
		LockAndModify(ByteBuffer mbb,int start,int end){
			this.start = start;
			this.end = end;
			mbb.limit(end);
			mbb.position(start);
			//创建新缓冲区
			buff = mbb.slice();
			start();
		}
		
		public void run(){
			try {
				FileLock fl = fc.lock(start, end, false);
				System.out.println("Locked : "+start+" to "+end);
				while(buff.position()<buff.limit()-1){
					buff.put((byte)(buff.get()+1));
				}
				fl.release();
				System.out.println("Release : "+start+" to "+end);
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		
	}
}