java RandomAccessFile 用法

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;

public class tmp
{
        public static void main(String args[]) throws Exception
        {
                RandomAccessFile random = new RandomAccessFile("first.java", "r");
                random.seek(10);
                byte[] data = new byte[1024];
                int len = 0;

                len = random.read(data, 0, data.length);
                System.out.println(new String(data, 0, len));
                random.close();
        }
}