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();

    }

}