package FileDemo;

 import java.io.IOException;

 import java.io.RandomAccessFile;

 public class RandomAccessFileDemo {

     /**

      * @param args

      * @throws IOException

      */

     public static void main(String[] args) throws IOException {

         writeAccess();

         readAccess();

         randomWrite();

     }

     // 随机写入数据，可以实现对已有数据的修改,因为可以使用seek()方法改变文件指针的位置

     private static void randomWrite() throws IOException {

         RandomAccessFile raf = new RandomAccessFile("random.txt", "rw");

         raf.seek(8 * 4);//将文件指针移动到指定位置

         System.out.println(raf.getFilePointer());

         raf.write("Ruby".getBytes());

         raf.writeInt(99);

     }

     private static void readAccess() throws IOException {

         RandomAccessFile raf = new RandomAccessFile("random.txt", "r");

         System.out.println(raf.getFilePointer());

         raf.seek(8);// 用于实现随机读取文件中的数据，数据最号有规律

         System.out.println(raf.getFilePointer());

         byte buf[] = new byte[4];

         raf.read(buf);

         String name = new String(buf);

         int age = raf.readInt();

         System.out.println("name=" + name);

         System.out.println("age=" + age);

         System.out.println(raf.getFilePointer());

     }

     private static void writeAccess() throws IOException {

         // rw:当这个文件不存在，会创建文件，当文件已经存在，不会创建，所以不会出现和输出流一样的覆盖

         RandomAccessFile raf = new RandomAccessFile("random.txt", "rw");

         raf.write("Java".getBytes());

         raf.writeInt(97);

         raf.write("python".getBytes());

         raf.write(98);

         raf.close();

     }

 }