java_randomAccessFile类的使用

package randomAccessFIle;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Arrays;

public class randomAccessFile{

    public static void main (String[] args) throws IOException {
        File demo=new File("demo");
        if(!demo.exists())
            demo.mkdir();
        File file=new File(demo,"raf.dat");
        if(!file.exists())
            file.createNewFile();
         RandomAccessFile raf=new RandomAccessFile(file,"rw");
         System.out.println(raf.getFilePointer());
         
         raf.write(‘A‘);//只写一个字节
         System.out.println(raf.getFilePointer());
         raf.write(‘B‘);
         
         int i=0x7fffffff;
         //用write方法一次只能写一个字节，把i整个写进去要write四次
         raf.write(i>>>24);
         raf.write(i>>>16);
         raf.write(i>>>8);
         raf.write(i);
         System.out.println(raf.getFilePointer());
         
         raf.writeInt(i);
         String s="李";
         byte[] gbk=s.getBytes("gbk");
         raf.write(gbk);
         System.out.println(raf.length());
         
         //读文件，必须把指针移到头部
         raf.seek(0);
         //一次性读取，把文件中的内容一次读到字节数组里
         byte[] buf=new byte[(int) raf.length()];
         raf.read(buf);
         System.out.println(Arrays.toString(buf));
         for(byte b:buf){
             System.out.println(Integer.toHexString(b&0xff)+" ");
         }
         raf.close();
    }
}