Java之文件的随机访问和读写RandomAccessFile

 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();
     }

 }