RandomAccessFile类的使用(随机读取java中的文件)

package coreJava;

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

public class RandomAccessFileWriteandRead {

public static void main(String[] args)throws IOException {
// TODO Auto-generated method stub

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");
//获取指针的位置：
System.out.println(raf.getFilePointer());

raf.write('A');//只写了一个字节
System.out.println(raf.getFilePointer());
raf.write('B');

int i = 0x7fffffff;

//用write方法一次只能写一个字节。如果要把i写进去的就得写四次
raf.write(i>>>24);//高8位
raf.write(i>>>16);
raf.write(i>>>8);
raf.write(i);
System.out.println(raf.getFilePointer());
//可以直接写一个int
raf.writeInt(i);
String s = "中";
byte[] gbk = s.getBytes("gbk");
raf.write(gbk);
System.out.println(raf.length());

//读文件必须把指针移动到头部
raf.seek(0);

//一次性读取
byte[] buf = new byte[(int)raf.length()];
raf.read(buf);
System.out.println(Arrays.toString(buf));
for(byte b:buf){
System.out.print(Integer.toHexString(b & 0xff)+"  ");
}
String s1 = new String(buf);
System.out.println(s1);

//关闭文件
raf.close();

}

}